[FlawlessTouch]

I haven’t worked with Blue Tansy, but I do know with plant extracts PH can change the colour quite drastically. Have you checked if the PH has changed between formulating it and when it turns green? If so it might be worth adding a PH buffer.

In terms of the smell, you could try using an odour masking agent - this is what I do for a serum I make with mushroom extract which leaves things smelling a bit odd.