From BiblePortal Wikipedia

Webster's Dictionary [1]

(1): ( n.) Of a red color; red, or reddish; as, a ruddy sky; a ruddy flame.

(2): ( n.) Of a lively flesh color, or the color of the human skin in high health; as, ruddy cheeks or lips.

(3): ( v. t.) To make ruddy.

King James Dictionary [2]

RUD'DY, a.

1. Of a red color of a lively flesh color, or the color of the human skin in high health. Thus we say, reddy cheeks, ruddy lips, a reddy face or skin, a ruddy youth and in poetic language, ruddy fruit. But the word is chiefly applied to the human skin. 2. Of a bright yellow color as ruddy gold. Unusual.

Holman Bible Dictionary [3]

 1 Samuel 16:12 1 Samuel 17:42 Song of Solomon 5:10 Lamentations 4:7 Genesis 25:25

Wilson's Dictionary of Bible Types [4]

 Song of Solomon 5:10 (c) This is probably used symbolically to describe the health, vigor, youthfulness and loveliness of the Lord Jesus Christ This same expression was used of David also in1Sa  16:12.

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [5]

( אִדְמוֹנַי , Admoni , Reddish ; Sept. Πυῤῥάκης ; Vulg. Rufus ) . Many interpreters think that the word means Red - Haired. and it is so rendered in the ancient versions, although ours understands A Ruddy Complexion. It would then appear that Esau ( Genesis 25:25) and David ( 1 Samuel 16:12) had red hair, a peculiarity so uncommon in the East that it forms a particular distinction, as in the Scriptural instances; but it is by no means unknown, especially in mountainous countries. It has been observed in Persia, accompanied with the usual fresh complexion. Such hair and complexion together seem to have been regarded as a beauty among the Jews. The personal characters of Esau and David appear to agree well with the temperament which red hair usually indicates. That interpretation, however, is by no means established, and the contempt of Goliath for David as a youth of a fair, bright skin is more probable. (See David). This view is confirmed by the application of kindred words, as Adam ( אִדִ ם ), in  Lamentations 4:7, to the Nazarites in general; and Adam ( אָדֹ ם ) to the bridegroom ( Song of Solomon 5:10), who is immediately described as black-haired ( Song of Solomon 5:11).

International Standard Bible Encyclopedia [6]

rud´i ( אדמוני , 'adhmōnı̄ (  1 Samuel 16:12;  1 Samuel 17:42;  Genesis 25:25 the Revised Version margin), אדם , 'ādhōm ( Song of Solomon 5:10 ); verbs אדם , 'ādham ( Lamentations 4:7 ), and ἐρυθριάω , eruthriáō , "to blush" (Ad Est 15:5)): "Ruddy" is the form taken by the adjective "red" when used as a term of praise of the human skin, and this is its use in the Bible (the Hebrew and Greek words are all usual words for "red" or "to be red"). The dark-skinned Hebrews found great beauty in a clear complexion.