I sourced a black woven felt called Melton ME313 from Hainsworth some years back, not sure it's still available. It's 1mm thick and coloured all the way through but works well as long as you are prepared to ream out the holes if required. It isn't as easy to work with as the scarlet felt, much more difficult to see what you are doing, for one thing....
https://www.hainsworth.co.uk/collections/melton/