Color picker outdated? more options are supported, including transparent

[Kavukamari]

on the UAP documentation, there are many more options available for the background color attribute, as indicated on this list here
UAP Remarks

the only option I specifically want is transparent, I do not like flat color backgrounds. I have been able to manually edit my manifest files for some tiles, and they have turned transparent, but it's inconsistent whether it works or not.

if this official color list was built into the program, I think the results would be more expected. At least adding transparent as a supported option would be incredibly useful

I know this hasn't been updated in 2 years, but this is the only feature this program is missing for me to consider it a perfect option.