Thank you for your suggestion! We will make a note, but I'm sorry to say that at this time we are not planning any changes to Explore mode. If you have a tricky trace, have you tried using Explore mode as the color for the branch that you don't want to trace and using the normal tracing color for the real branch? You can easily remove the Explore mode branch by hitting the "Discard" button before you submit your trace.
If you'd like more color contrast, you can also change the color of your paint in the 2D section under the "Settings" menu (click the gear icon at bottom right).