I'm a bit puzzled by "chromatic in G". Surely if they are CHROMATIC, they have all the sharps/flats in which case they can handle any key.
If on the other hand they can only manage G-A-B-C-D-E-F#-G they are DIATONIC in the key of G. The only other arangement would be if the accidentals were in a separate row or something.