I reckon it's the 'whiteness' of natural undyed maggots that puts fish off - it seems to 'spook' them on occassions. On a small river I found a small shoal trout and hand fed them with some 'mixed' maggots and watched the shoal's reaction.
Red and orange maggots were their favourites then yellow, green ones were totally ignored, but white ones initially spooked them as they descended the water column - when they hit the bottom the fish's interest would return and they'd move over them to investigate but keep their eyes open to readily intercept any more attractive descending coloured samples.
When there was a 'carpet' of whites in the gravel, the trout would move over them to 'graze' - using the waft of their fins to lift them off their resting places - before spinning back and snatching them as they started to re-descend.
This aversion to taking stationary baits off the bottom and trying to make them float-up might explain why I used to catch so many parr foul-hooked in the pectoral and caudal fins!
I've repeated this experiment on finding shoals of chublets - same results and behaviour but observations usually terminated by the moving-in of a larger specimen scattering the shoal!
Since then, if I'm planning on a trotting session, I'll usually take bronzies if I can get them, or a half and half mix of reds and plain, which turn off-white by dye transfer in the bait-tub.