Create .mintty folder with subfolder themes in c:\Users\< >
Example:
C:\Users\sandeep\.mintty\themes
Download '.minttyrc' files from https://github.com/iamthad/base16-mintty and add them to themes folder.
Open git bash for windows --> options --> theme dropdown
I removed the base16- prefix from the the themes and made a base16 dir and moved
them, looks neat, then shipped them to the ./mintty/themes dir for mintty to source
great superb themes