Changing Footer background colour and font

HI
Every time I change my footer background colour and font colour in the Appearance > customise menu, and save it, although it changes in the customiser, it does not change on my live webpage when I reload it.

When I go back into customiser again, it has reverted to its previous colour!

Help! All I want to do is change the dark/black footer in Minimal Grey to pale grey. I like all of the rest of the Minimal Grey colours so I dont want to have to customise everything.

Thanks
Jane