By default GIMP has a checker bord pattern built up of mid tone gray checks. You can however change that in the drop down menu.
![]() | That white, black and gray only checks disables checks and the transparency will be shown as a solid black, white or gray color. |
The size of the checks in the pattern that indicates transparency.
![]() | If you have set the checker type to white, gray or black only then then the size will have no effect what so ever. |
If you are working on an 8-Bit display, the GdkRGB subsystem of GDK will automatically figure out if it needs to install an own colormap or not. However since GIMP's plug-ins are all separate processes with their own instances of GdkRGB if may happen that GIMP and some of it's Plug-Ins choose different colormaps, resulting in color flickering.
If you encounter such behaviour, you can activate "Install Colormap" in order to force GIMP and it's Plug-Ins to use the same colormap.
If you are working on an 8-Bit display, you can display the "Marching Ants" which show the current selection by means of a rotating colormap instead of re-drawing them all the time.