Basically, the idea is to make a word that probably isn't a word, but very well could be, if you were to show it to a linguist who specializes in Latin, Ancient Greek, and English, and they liked it.
For example, the probably-not-a-word-but-so-totally-could-be I just made up is "caerulidescent", meaning "sky-blue-ish", from the real word viridescent, meaning "greenish", and the Latin word caeruleus, meaning "sky-blue". Pronounced "kah-rule-ee-deh-scent".
I've got a few more of the color ones:
Rubidescent, reddish, from ruber, red
Herbidescent, grass-ish, from herbeus, grass-colored
Nigeredescent, blackish, from niger, black
Albidescent, whitish, from albus, white
Fulvidescent, yellowish, from fulvus, yellow
Lutedescent, also yellowish, from luteus, yellow
Purpuridescent, purplish, from purpureus, purple
And I have one non-color one: Amaschalagniphobia, meaning "the fear of not being sexually attracted to armpits". I'll let you figure out the breakdown on that one.
Updated by Mantikor