Any tips on color mixing/color switching with 3 into 1 A10T?

[Sodium100mg]

I'm trying to understand the 3 into 1 extruder. When I mix 90% white to 10% black, the color doesn't so much mix as print next to each other, so one side of the print is much darker than the other side.

When switching between red and white, my priming pillar is 2.5cm and the red still bleeds into the white.

Any tips to improve color mixing and color switching would be appreciated.