Yeah, the original fluff concept was that Blood Axes thought imperial camo was some sort of lucky/symbolic/mystical pattern - it never occurred to them that camo made it harder for an enemy to see you, coz why would an ork not want to be seen?
This explained why some Blood Axes and their vehicles would copy Imperial camo patterns but often in bright colours to stand out more on the battlefield
No doubt some Blood Axes do think this way, but others (e.g. Kommandoes) seem to perfectly well understand the combat benefit of staying unseen until the right moment.
I agree with Alex re checker patterns - they're for Goffs.