I disagree with the proposed solution. I agree that 1, 6 or 8 are the only possible options. The number of hexagons doesn't form a pattern (2,2,3 and 1,1,3) so ignore this. The colours of the hexagons in the third panel are determined by the preceding panels (red & blue, red, red & blue and blue, blue, blue) The third row's colours are black, red & blue so the third panel should have all three colours - hence the solution should be option eight. It's not a hugely satisfying solution but I think my logic is slightly more robust. I came here with a similar problem and the same logic applies - this one follows the same rules, it's vertically oriented instead of horizontally.