[list] How to get the list of all installed color schemes in Vim?

i know i am late for this answer but the correct answer seems to be

See :help getcompletion():

:echo getcompletion('', 'color')

which you can assign to a variable:

:let foo = getcompletion('', 'color')

or use in an expression register:

:put=getcompletion('', 'color')

This is not my answer, this solution is provided by u/romainl in this post on reddit.