From BiblePortal Wikipedia

Wilson's Dictionary of Bible Types [1]

 Exodus 25:4 (c) Blue threads were woven into the various parts of the tabernacle to remind Israel that though they were traveling on earth their destination was Heaven. The color "blue" is used throughout the Scripture to remind the people of their heavenly character. The blue yarns were woven in with the red yarns to remind Israel that they were forgiven and were made fit for Heaven by the shed blood of the sacrifice. Linen yarns also were woven with these to remind the people of GOD of GOD's righteousness given to them as a gift to make them acceptable to GOD. Purple yarns were to remind Israel that they were a part of the royal family of Heaven. The cherubims were to remind them that one day they would be associated with angels. See also  Exodus 26:1;  Exodus 39:3.

 Exodus 26:31 (c) The colors in the veil were to remind Israel that they could not enter the holy place, nor have the full enjoyment of GOD's fellowship except by the graces and privileges represented by these.

 Exodus 26:36 (c) The blue in these door curtains was to remind Israel that they could always enter into GOD's house and GOD's fellowship by means of that heavenly revelation and heavenly salvation provided through the blood of the lamb.

 Exodus 28:31 (c) This color on Aaron was to remind him that he was always to be enveloped with a heavenly deportment. It would also remind him and Israel that he was a heavenly man living in heavenly places and occupied with heavenly business.

 Numbers 15:38 (c) The sabbath breaker had just been stoned (see  Numbers 15:35), so GOD told His people to put this ribbon of blue on the bottom of their garments to ever remind them that they were to obey the message from Heaven, and not live by their own ideas, and conclusions.

 Esther 1:6 (c) The wicked king seeking to justify his sins had the blue woven in the curtains so as to connect his evil orgies with something of Heaven and Heaven's business. Most wicked practices have in some way a religious tinge to their ceremonies. The most wicked institution in the world, the apostate church, has a great religious program in order that they may cover up their evil doings by it.

 Esther 8:15 (c) It is evident that Mordecai was GOD's man for that particular time. The blue would remind all who saw him that he was carrying out GOD's plan, and accomplishing GOD's purposes.

 Ezekiel 23:6 (c) The Assyrians clothed themselves in garments of blue probably to imitate the priesthood of Israel and thus give a religious touch to their evils. Thus with a pretext of being a godly people, they would deceive Israel and gain their confidence. Wicked religions still follow this plan.

Webster's Dictionary [2]

(1): (superl.) Literary; - applied to women; - an abbreviation of bluestocking.

(2): (superl.) Pale, without redness or glare, - said of a flame; hence, of the color of burning brimstone, betokening the presence of ghosts or devils; as, the candle burns blue; the air was blue with oaths.

(3): (superl.) Low in spirits; melancholy; as, to feel blue.

(4): (superl.) Having the color of the clear sky, or a hue resembling it, whether lighter or darker; as, the deep, blue sea; as blue as a sapphire; blue violets.

(5): (superl.) Suited to produce low spirits; gloomy in prospect; as, thongs looked blue.

(6): (n.) One of the seven colors into which the rays of light divide themselves, when refracted through a glass prism; the color of the clear sky, or a color resembling that, whether lighter or darker; a pigment having such color. Sometimes, poetically, the sky.

(7): (v. t.) To make blue; to dye of a blue color; to make blue by heating, as metals, etc.

(8): (n.) A pedantic woman; a bluestocking.

(9): (superl.) Severe or over strict in morals; gloom; as, blue and sour religionists; suiting one who is over strict in morals; inculcating an impracticable, severe, or gloomy mortality; as, blue laws.

(10): (pl.) Low spirits; a fit of despondency; melancholy.

Holman Bible Dictionary [3]

tekeleth  Ezekiel 23:6 Jeremiah 10:9 Exodus 25:4 Exodus 26:1 26:4 Numbers 4:6-7 4:9 Numbers 15:38 2 Chronicles 2:14 2 Chronicles 3:14 Exodus 28:5-6 28:8 28:15 Exodus 39:1PurpleColors

Morrish Bible Dictionary [4]

This colour was used extensively in the hangings of the tabernacle; in the vesture of the priests; and in the coverings of the vessels of the tabernacle when they were being removed. The colour is typical of heaven: the whole of the tabernacle was "a shadow of heavenly things."  Exodus 26:28 : etc.

King James Dictionary [5]

BLUE, a. blu. One of the seven colors, into which the rays of light divide themselves, when refracted through a glass prism. There are various shades of blue, as sky-blue, or azure, Prussian blue, indigo blue, smalt blue, &c.

Prussian blue, a combination of the oxyd of iron with an acid called ferro-prussic.

Easton's Bible Dictionary [6]

 Exodus 25:4 26:1,31,36 Exodus 28:31 Numbers 4:6,7,9,11,12Colour

Hastings' Dictionary of the Bible [7]

BLUE . See Colours, 5 .

American Tract Society Bible Dictionary [8]

See Purple .

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [9]

( תְּכֵלֶת , Teke'Leth), almost constantly associated with purple, occurs repeatedly in Exodus 25-39; also in  Numbers 4:6-7;  Numbers 4:9;  Numbers 4:11-12;  Numbers 15:38;  2 Chronicles 2:7;  2 Chronicles 2:14;  2 Chronicles 3:14;  Esther 1:6;  Esther 8:15;  Jeremiah 10:9;  Ezekiel 23:6;  Ezekiel 27:7;  Ezekiel 27:24; Sept. generally Ὑάκινθος , Ὑακίνθινος , and in  Sirach 40:4;  Sirach 45:10;  1 Maccabees 4:23; and so Josephus, Philo, Aquila, Symmachus, Theodotion, Vulgate, and Jerome. (In  Esther 1:6, the word translated " blue" is the same elsewhere rendered " linen.") This color is supposed to have been obtained' from a purple shell-fish of the Mediterranean, the conchylium of the ancients, the Helix ianthkna of Linnaeus (Syst. Nat. t. i, pt. 7:p. 3645; and see Forskal's Descriptio Animal. p. 127), called chilzon ( חַלְזוֹן ) by the ancient Jews. Thus the Pseudo-Jonathan, in  Deuteronomy 33:19, speaks of the Zebulonites, who dwelt at the shore of the great sea, and caught Chilzon, with whose juice they dye thread of a hyacinthine color. The Scriptures afford no clew to this color; for the only passages in which it seems, in the English version, to be applied to something that might assist our conceptions are mistranslated, namely, "The blueness of a wound" ( Proverbs 20:30), and "A blue mark upon him that is beaten" ( Sirach 23:10), there being no reference to color in the original of either. The word in the Sept. and Apocrypha refers to the hyacinth; but both the flower and stone so named by the ancients are disputed, especially the former. Yet it is used to denote dark-colored and deep purple.

Virgil speaks of ferrugineos hyacinthos, and Colunella compares the color of the flower to that of clotted blood, or deep, dusky red, like rust (De Re Rust. 10:305). Hesychius defines Ὑακίνθινον , Ὑπομελανίζον , Πορφυρίζον . It is plainly used in the Greek of Ecclus. xl, 4, for the royal purple. Josephus evidently takes the Hebrew word to mean "sky-color;" for in explaining the colors of the vail of the Temple, and referring to the blue ( Exodus 26:31), he says that it represented the air or sky (War, v, 4); he similarly explains the vestment of the high-priest (Ant. 3: 7, 7; and see Philo, Vita Mosis, 3: 148; t. ii, ed. Mangey). These statements may be reconciled by the fact that, in proportion as the sky is clear and serene, it assumes a dark appearance, which is still more observable in an E stern climate. (See Purple).

The chief references to this color in Scripture are as follows: The robe of the high-priest's ephod was to be all of blue ( Exodus 28:31); so the loops of the curtains to the tabernacle ( Exodus 26:4); the ribbon for the breastplate ( Exodus 28:28), and for the plate for the mitre ( Exodus 28:37; comp.  Sirach 45:10); blue cloths for various sacred uses ( Numbers 4:6-7;  Numbers 4:9;  Numbers 4:11-12) the people commanded to wear a ribbon of blue above the fringe of their garments ( Numbers 15:38); it appears as a color of furniture in the palace of Ahasuerus ( Esther 1:6), and part of the royal apparel ( Esther 8:15); array of the idols of Babylon ( Jeremiah 10:9); of the Assyrian nobles, etc. (Ezra 23:6; see Braunius, De Vestitu, i, 9 and 13; Bochart, 3:670). (See Color).