Q.leaf color
I have had my croton plant for 2 years – still have a few original leaves. Have lots of new leaves but they are all green with some yellow. What gives?

For good color in your Croton, they need good nutrition. They are acid loving tropical plants. Feeding them 3 times a year with an acid producing fertilizer will help.
Proper sunlight, bright but not direct and consistently moist soil.
https://www.gardeningknowhow.com/houseplants/croton/care-croton-plants.htm