Fix serialisation of color dicts

[tomvanmele]

What type of change is this?

• Bug fix in a backwards-compatible manner.
• New feature in a backwards-compatible manner.
• Breaking change: bug fix or new feature that involve incompatible API changes.
• Other (e.g. doc update, configuration, etc)

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• I added a line to the CHANGELOG.md file in the Unreleased section under the most fitting heading (e.g. Added, Changed, Removed).
• I ran all tests on my computer and it's all green (i.e. invoke test).
• I ran lint on my computer and there are no errors (i.e. invoke lint).
• I added new functions/classes and made them available on a second-level import, e.g. compas.datastructures.Mesh.
• I have added tests that prove my fix is effective or that my feature works.
• I have added necessary documentation (if appropriate)

[codecov]

Codecov Report

Attention: Patch coverage is 76.92308% with 3 lines in your changes missing coverage. Please review.

Project coverage is 61.37%. Comparing base (663a05c) to head (2196a44).
Report is 15 commits behind head on main.

Files with missing lines	Patch %	Lines
src/compas/colors/colordict.py	76.92%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1408      +/-   ##
==========================================
+ Coverage   60.71%   61.37%   +0.66%     
==========================================
  Files         207      207              
  Lines       22268    22275       +7     
==========================================
+ Hits        13519    13671     +152     
+ Misses       8749     8604     -145     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[chenkasirer]

LGTM