See Reddit Post

yovliporat:
"Since mana powder can be made with the different coloured floral powders, and throwing a floral powder into a pool changes its colour, trying to make mana powder with a floral powder will result in the colour of the pool changing. Not really a bug, but... I wanted endoflames, not a magneta pool :("

I have the same thing (Most recent version of botania: R1.8 242), it does however make the powder... It is however, a fun feature to have (Almost like a disco mana pool)