Python 2.5.1 for windows
When I change the cursor color to another color, it still stays black, so I can't really make black background.

IDLE on Windows appears to be using an always-black caret (cursor) - not the standard caret behavior, which does its "blinking" by inverting the background color.
So something might be improved here, but I doubt you can reliably set the caret color on Windows; see http://support.microsoft.com/kb/84054/en-us

The page on the link says you can invert it. As I understand, the caret color is either black or background color. You could force it to be black/white.

Also you should hide this option in selector - it's misleading, because I thought i does something.

AFAIK you can - you simply have to restart IDLE after changing the color and saving the changes.

This is a known issue with Tk's Text widget, which IDLE uses.

> AFAIK you can - you simply have to restart IDLE after changing the color
and saving the changes.

Thanks, I found that out already. Maybe then after I change that option (and perhaps some others) IDLE should say "Please restart IDLE for some changes to take effect" ?

I just found out that this has nothing to do with Tk's Text widget, which is fine.

I'll be submitting a patch to fix this issue in a short while.

Fixed in patch 1725576.