"I don't see why not," has gotten me in trouble many times. Probably a lack of vision augmented by beer goggles. I hope this time yours works out well.
Here is a mock-up of entry point placement graphics, with the default palette this time.
The current background is set to color 8, as is entry point 8 which is just above the arrow.
EPoint1 shows the background is set to color 1 (black), and the entry point markers set to colors 2-9 instead of 1-8.
I can't find where the background color is set in the source code, but if you can it should be a pretty easy fix. (I'm still lousy at reading code.)