Why are my plugs all different colours?

[IBLOWN]

those plugs are way rich,
if the air cleaner is cleaned and theres no restrictions/blockages
anywhere in the air box and the injectors are fine
then you'll probably need to adjust your fuel maps.
maybe give it a dyno.

Its actually booked in for a PC V in the next few weeks but wanted to sort out this problem first.

It definately has a problem if the richness is getting worse over time. Tuning would be a waste of time until its fixed. The tune will just go out of whack again.