| Keyboard Shortcut | Menu Shortcut | Menu Location |
| Ctrl+PgUp | Alt+I, I | Image -> Increase Color Depth |
The Increase Color Depth command increases the number of bits per pixel, which controls the maximum number of colors the image can contain.
Activate the Increase Color Depth command. Set the desired color depth, and click OK.

Bpp
Color depth in bits per pixel.
This command is only effective when you select a color depth greater than the image’s current color depth. For example, “increasing” a 24 bpp image to 8 bpp has no effect. The current color depth is shown in the Image Mode status bar.