Hello @mjkruzel3 this reply is also for @cn9ne …ok so I managed to build this:-
Which allows you to control if you want to show the months, the weekdays, allows you to display this in horizontal or a vertical layout, you also get to control the gutter size (square cell size) as these are SVGs you can create your own custom themes from scratch. The stuff you can’t customise via a powershell parameter you can customise via CSS. I will stick all this into a blog post on how to use this new custom component. I have not pushed it to the powershell gallery, but very confident this will solve your problem on customising a specific cell colour, as this is all controlled via CSS.
I know I am not giving you the answer to your initial question, but I am showing you the potential of this new component that does do what you are asking.
I just put this component on the powershell gallery which in-turn will sync to the UD marketplace. I also wrote a blog on this component here:- https://psdevuk.github.io/ud-flix/GitHub-Styled-HeatMap-Contribution-Calendar/