Color module not working

I am having problems with themes where the color module options are enabled. Changing the options on the wheel has no effect, and I get a couple of error messages, including "warning: getimagesize() [function.getimagesize]: Read error! in /home/sitename/drupal_html/modules/color/color.module on line 263."

I have uploaded a fresh color module file to the server, in case the original has got corrupted somehow, but the problem still occurs. It is happening with both simpla and garland themes.

Grateful for any ideas anyone might have.

Thanks