... try to colour the brown parts with other 'inverse' colour(s) like dark purple and/or dark green.
'Black' is mostly a mixture of several colours/pigments, averaging to 'nearly' black ... if one or more of the pigments aren't absorbed, you'll see this colours ...
Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [
reprap.org] -- Deutsche Facebook-Gruppe - [
www.facebook.com]
Call for the project "garbage-free seas" - [
reprap.org]