feat: Background color configuration for the cluster marker

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Fixes #635 🦕

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[codecov[bot]]

Codecov Report

Merging #636 into master will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #636   +/-   ##
=======================================
  Coverage   53.08%   53.08%           
=======================================
  Files          12       12           
  Lines         486      486           
  Branches       73       73           
=======================================
  Hits          258      258           
  Misses        228      228

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