6 wire steppers have 4 coils arranged in 2 pairs of 2, with each pair having a shared tap. You need to measure with a meter resistance between different combination of leads to find the appropriate pairings. Resistance between the center tap and either end of the pair of coils should be X ohms. Resistance between both ends of a pair of coils should measure 2 * X. If it measures very high resistance or open, then those two wires are of opposite pairs of coils. Based on your previous statement, I'd start off with brown and orange being the center taps.