One way to add color to a README is by utilising a service that provides placeholder images.
For example this Markdown can be used:
- ![#f03c15](https://via.placeholder.com/15/f03c15/f03c15.png) `#f03c15`
- ![#c5f015](https://via.placeholder.com/15/c5f015/c5f015.png) `#c5f015`
- ![#1589F0](https://via.placeholder.com/15/1589F0/1589F0.png) `#1589F0`
To create a list of any colors you like:
-
#f03c15
-
#c5f015
-
#1589F0