Brian Mitchell writes
It seems to me that when the flowers first open the stamens are a
creamy yellow and when they've been sufficiently visited by pollinators
they turn orange/brown

But is that a result of being visited by pollinators or is that simply
an ageing thing?

For example, my hippeastrum anthers start long and closed up, they
split open and curl back to reveal the pollen, which steadily gets
darker and duller yellow in colour, then finally the stigma curls back
towards the anthers to effet self-pollination - ie the colour change
happens even though the (indoor) hippeastrum hasn't been pollinated.

--
Kay