Number of Colors # validation issue

[eladisimo]

When setting 2D->Number of colors, the limit it to minimum of 2 colors, effectively prevents users from setting it to 10 (for example) after setting to anything that begins with 2, because the first digit doesn't accept "1".

one approach would be to put a slider (better than a numeric spinbox!).
another would be to have the input validation done on context exit from the text box and not on any key input, and then you paint it in red and put a remark on above/below that the value is too low.

the workaround I found it to copy the value I wanted from another box/text (e.g. 16) and paste it there, but that's probably not what you meant.

steps to reproduce:

1. go to 2D tab, number of colors field
2. set value to anything other than 1
3. try to type 10