ColorMount is not my personal fave either, but it does seem to work on my fiber as well as BufferMount. You might try playing with the temperature and pressing times to see if it will work for you – I've used same as BufferMount.
I haven't bought tissue in a few years. I'm still using MT-5, and ArchivalMount, as well as BufferMount. Are you saying that ColorMount is the only tissue available now?