i think that there is no problem : there will still be 1 RAC per LAC. Indeed, when there is a change of LAC, even if the RA code and colour are identical, the “routing area identity” is changed
(RAI = LAC + RAC)
So it should be safe to do that (1 RAC for the whole network). Any other opinion on the matter are welcome !
However I never tried this. To play safe, I always preferred to distinguish rAcode and RAcolor between different LAC.