Simple Color Wrap: A5-6, B2-6, D6-6, E8-6, F1-6, H4-6, I7-6 on 6
Coloring is a unary (single value) forcing chain of regions with two places for 6, so 6 must either be in the greens or the blues. Hence any 6 that sees two colored 6's is history:
Therefore we can remove A1-6, B9-6, C5-6, C8-6, D2-6, E4-6, F7-6, H9-6, I6-6.