acutally the idea of leaving it alphabetically sorted is that its easier to find the colour you're looking for because you would probably only know the name which is what the app is for...
Would it be useful to sort it by colour? If so, that would be a little complex, how would i do that?
If you want to give the user an easy way to find a color by name, you should add a Search-field; preferably one that filters the items while the user is typing. You could also make it more intelligent by automatically interpreting "grey" as "gray".
EDIT: if the user types "green", he would see all green colors (darkgreen, lightgreen, ...), which you can't do with regular alphabetic sorting.