I would have sworn I posted a question about this on the forum, but darned if I can find it. I was trying to use a player to highlight text in graphics 0. I ran into trouble with not being able to see the text. I played with PRIOR to move the PM back and forth with the playfield layer with no luck.
Tonight I thought, maybe the player color is just too intense. I backed it down from 10 to 6, and presto it worked. IIRC the default luminance is 8 for text.
The screenshot is using PM double resolution with one player in each of the widths, and the 4th one is player4 single width but defined as 0xF instead of 0xFF (half width). So you can conceivably highlight 32 chars with proper player alignment. Maybe using the missiles combined as player 5 you could get all 40.