Hi Rich -- I think you mean the FGR.2? It depends on the variant you're doing, the kit offers options for camo or triple-grey schemes. The camo is the boxtop scheme and IIRC it depicts the aircraft at the time there was a third underside colour, before the camo went wraparound (as it did on Tornados) -- whether Phantoms got this latter is something I'm not clear on.
For the camo scheme, my best shot at this time is as follows (British Standard, equivalent of FS):
Dark Green BS381C/641 (Gunze H330)
Dark Sea Grey BS381C/638 (Gunze H331)
Using the Gunze codes you can work through comparison charts to find the nearest matches in other ranges, eg the charts at the IPMS Stockholme site. Humbrol and MM are the most likely to have matches, but if you can get samples of the colour there'salways the mixing road in acrylics. I know Humbrol have the three greys for the other scheme in their range.
Incidentally, Allmark have a high quality decal sheet featuring the same schemes and it's highly recommended as preferable to the kit sheet, crisper and better printed, with truer colours.
Cheers, hope this helps, Mike/TB379