The original atom had a fixed colour palette, like so
| Default | Used for: |
| Black | Text and 2-colour graphics |
| Green | |
| Black | Background |
| Dark green | Dark semigraphics |
| Green | 4-colour graphics |
| Yellow | |
| Blue | |
| Red |
This has now been made programmable. With only four colours in 160x120 resolution it is fairly limited for displaying images, but at least one is not stuck with the rather garish defaults. One could for instance have four shades of gray, which is a slight improvement on monochrome. For an antique effect, the palette could be set to four shades of sepia.
If you take a look at the Dilbert website, the weekday cartoons are grayscale. Saving as monochrome images reduces the quality significantly: the text appears coarser.
The text colour currently applies to the whole screen, so it isn't possible to have different coloured text on the same screen unless the palette is changed during the display period. This is rather tricky to do. Changing the text and background colour has some uses such as fading screens out then fading new ones in. And for getting operator attention for alarm conditions, the steady green text can be ramped through red intensities. Warning screens can be displayed in black on yellow.