How to edit jQWidgets png files?

Question

I'm using GIMP to do the editing in the png file I've shown below. On selecting one of the arrows and trying to paint it red, the colour just does not turn red. It stays grey. I'm just unable to make any changes to it.

I'm a newbie to using GIMP, so do let me know if it has something to do with the layers or channels etc. How do I alter the icons in the png file?

ps: The image is from one of the jQWidgets themes (MIT license)

Answer 1

This PNG file is in indexed color mode. This means that it only contains a limited amount of (different) colors, in its so-called color map. You can't use any colors other than those in GIMP as long as the image is in this mode. In this case, it is actually 77 times the same color, #CCCECC in HTML notation.

In order to remove this restriction, change the image mode to RGB in the Image -> Mode menu.