I speak towards your second sentence here. I agree to a point, and I disagree after that. It is true that every strain I have dealt with STARTS out green and change over to their color expression as early as about a 1/4-1/3 of the way into veg. Many of these strains are not coming from the common, everyday, seed market....That seems to be just about exclusive to purples. For the most part. Common market coloring strains begin coloring later and, for the most part, need a little push to get them really coloring......Not all of them but the majority is so. Remember that when you see those colored plants. The grower has that dialed in to express that trait.
The banana OG pheno I mentioned. Is one that really needs no help to yellow and it yellows pretty early in veg. Care must be taken to not overdo some nutrients in bloom, because the plant will not show it, in a conventional way. "Real" (not just prone to, but will to at least some extent, naturally color) Orange, Red, Blacks (of various degrees) and the more common purple strains,, are out there. Many come from unconventional breeders that you have and have not heard of.......It's up to you to find them!