Yes, I agree the major part of seedlings stay green. Others need good natural light to become colorful. My “Stoplight” never shows its true color, always green and dark, though when I got this variety it was excellent and colorful one.
Jeff, I agree with you, it takes time for crotons to reveal their potential. As for these young seedlings I can already say that high percentage of them will be colorful. Many Thai hybrids have green long and narrow first leaves. And those ones with twisted leaves may also have interesting foliage shape in the future.
Also much depends upon parenting plants. To get something distinguished, plants with quite diverse features should be hybridized. The result of spontaneous or self-pollination can be dull. Today we have hundreds of excellent varieties, big work has been already done. It only remains for us to use our imagination in hybridization to get something new and outstanding.
As for me it’s good luck to get seeds under electric light. There are not many opportunities for purposeful hybridization as two different crotons flower simultaneously rather rarely. It only remains to wait for a chance.