This is a very simple fisher package which colorizes the output of man which results in much nicer to read manual pages. It does so by simply setting some shell variables to colours. It's a shameless ripoff 😃 from omf-color-manual and was ported to fisher for use.
You should be able to install fish-color-manual via fisher.
$ fisher add pcr910303/fish-color-manualYou can download conf.d/color-manual.fish and source it from ~/.config/fish/config.fish if you want, but why would you? If you're one of the ones that don't use fisher, going to the original repo will be more beneficial.