Well yes moisture in the filament is one of the major root causes of nozzle oozing and stringing.
Multi color prints with high color contrast differences are always difficult and need perfect settings to minimize defects.
Recommendations from my side:
- Calibrate flow and K values for each of the filament colors since the different pigments can influence these characteristics even if the underlying base material is the same.
- Also do stringing tests for each and fine tune the retraction and nozzle z-hop and wipe settings.
- Try with Arachne instead of Classic Wall Generator as this can sometimes reduce the amount of z-hops and travels over the different colored areas. Note using “Avoid crossing walls” won’t help in such multi color areas since each color area is seen as a different entity by the slicer so will still cross over them.
- Manually painted areas usually go several layers deep and depth is not uniform across the part and there is no control over that (as far as I know). This significantly increases the amount of nozzle crossings of the different colors and with it the chances of having unwanted strings of the black material deposited into the white areas. Better would have been a design where the black color is its own object as an inlay to the white main part with a height of only one or two layers to the black colored inset.
- quality and appearance would be far better if the colored insets are done flush on the first layer(s) of the build plate (face down) but with this part design that would impact the appearance of the outer bevel area as well as screw hole recesses the latter of which would need supports if printed in this face down orientation while removing the need for supports on the connector recesses on the rear with the part orientation you currently have.