scripts: use color variables instead of escape codes

[casperklein]

Description

This PR streamlines the color usage of the scripts. Color variables are now globally defined in log.sh. I did not use a separate file like colors.sh, because some scripts only source log.sh

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Improvement (non-breaking change that does improve existing functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (README.md or the documentation under docs/)
• If necessary I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[polarathene]

i think it's clear from the variable name what the usage is

I'm not sure if that applies to ${RESET} though?

Depending on which PR gets merged first, might want to keep #2535 in mind since it's adding a bunch of new setup commands that would need to be converted.

[casperklein]

I'm not sure if that applies to ${RESET} though?

Standing alone, maybe not. But it's only used in context of color usage so I think it's fine.

[casperklein]

To not make things harder for #2535, I'll wait with merging this.

[georglauterbach]

If we, in the future, realize that we may need the prefix we can always add it :)