Thanks, yes switching to HDMI fixed the colours.
I'm still not happy with the text on my monitors. I'll run a fresh calibration on all of them and see if that helps.
I am happy with the performance though, everything feels faster including FCP. Hopefully that'll get even better when they bring out a version that uses Metal 2 on Mojave.
One thing I was hoping to do as soon as I installed it was to buy Pixelmator Pro as it needs a Metal compatible card. Turns out there is no way for them to check if a Metal card is available so you can't buy it on an older Mac Pro. I'll buy it on my MacBook Pro and copy it across.
I'm too lazy to read back right now, but are you running Mojave? If so, this likely explains your complaints about text: https://www.reddit.com/r/apple/comments/8wpk18/macos_mojave_nukes_subpixel_antialiasing_making/