The Nazarites were not literally white
When Lamentations speak of the Nazarites being purer than snow, and whiter than milk, it would be nice if you remembered you are reading the book of LAMENTATIONS!!!
The passage is referring to their former condition of commitment, and vows of purety towards YAH. The Messaiah himself is said to have been a Nazarite from the womb (pure, sinless). Whiter than snow is another way of saying they were righteous..As our sins also are washed away white though they were as scarlet. We are also called to keep ourselves unspotted from the world.
As for the scripture saying they were ruddy in body
4:5 They that did feed delicately are desolate in the streets: they that were brought up in scarlet embrace dunghills.
7 Her Nazarites were purer than snow, they were whiter than milk, they were more ruddy in body than rubies, their polishing was of sapphire:
8 Their visage is blacker than a coal; they are not known in the streets: their skin cleaveth to their bones; it is withered, it is become like a stick.
Definition of visage1: the face, countenance, or appearance of a person
2: ASPECT, APPEARANCE
So you see, the appearance of the Nazarite were blacker than coals. Keep in mind, the bible doesn't boast in the doctrine of white superiority as some will have you believe. The bible says no flesh will glory in his sight, so keep that in mind when false teachers who are secretly or not so secretly trying to convince you white skin means you're pure. This scripture has nothing to do with having white skin! In fact, if you literally had white skin , Israel would have thought you to be a leper.