[Coldfire]

When they are young they are more of a silver color, black spots with red bellies, but that will change to a olive green color, their spots will slowly fade, the red may or may not still be as bright. During their juvenile development their eyes will gain a red tint, and slowly darken. As they approach adult color, they will develop a deeper olive color, and silver and gold specks as if they had be dusted with glitter.

During sexual maturity they will become solid black.

 

[Coldfire]

Yeah, most of their color change will happen around the 6" mark or so. I know that they develop the red eye tint early, but the olive color, fading spots, and specks of silver and gold come around the 6" lenght. Of course, each fish will develop differently, but in general that is when.