It's a deep blue

That means its inverted

This isn't "really" possible. Yes it inverts slightly to your eye, and I'm not sure how that works, it's similar to how if you look down on the screen from top at a 45* angle it also appears inverted. If you max out the contrast wheel of any gameboy with backlight it will do this. whatever the screen looks like when you drag your finger down the wheel is the correct polarization. don't go all the way up because it doesn't really invert. it's not magic, but it is some sort of illusion

So are you saying that all backlight/inverted gameboys can un-invert with the contrast wheel?

My other gameboy that's modded with a LEDx3 is uninverted, but it's contrast wheel doesn't take it to inversion, it just makes the screen fully black/white at it's max setting.
The default/comfortable position on its contrast wheel is the same position that is displays a comfortable, non-inverted view on my new gameboy.

The contrast wheel does something like this:
100% up: blank
75% up: Low contrast non-inverted
50%: Crisp, non-inverted
35% down: High contrast, inverted
25% down: Inverted
100% down: blank

It's a pretty nifty illusion I suppose!
I'm going to try to replicate it on my next gameboy.

did you mess with the contrast wheel before modding it?  its not unusual for the contrast to do this, on stock consoles.  the parts on the consoles are just reaching the end of their life, electromechanical parts like this are rated in the # of movements as well, they just wear out.  and start behaving badly.

if the backlight caused this, and you're sure it wasn't there before, dunno.

Hm, that could be it. I did play with this particular gameboy quite a bit before I actually modded it, and I don't have any memory of the contrast wheel taking it to inversion, but then again, I probably wouldn't have much reason to ever change the contrast so much.

On the other hand, when I put it back together post-backlight, the very first thing I noticed was that the contrast wheel was very, very sensitive.  It'd be a bit weird that I hadn't noticed that before, but who knows?

Also, I'm not sure if it's important at all, but after adding the polarizing film the neutral screen color (powered off) became a deep blue instead of the olive green it had been before, which seemed a bit strange to me.

if the backlight caused this, and you're sure it wasn't there before, dunno.

Which color backlight did you go with? Just out of curiosity.

Mint. It looks fantastic. it's really bright and really well-diffused. I also swapped the buttons with a set of translucent purple/brown-ish ones from the craaAAaazy custom mold thing that was on Kitsch a while ago.

I just recently modded my clear Play It Loud DMG with a backlight and prosound. I used Nonfinite's V3 Ultra backlight, as well as an extra square of polarizing film I bought from his store.

When I got the gameboy all put back together I noticed that the contrast wheel now has the ability to take the gameboy screen through a spectrum from normal colors on one end, to inverted (negative) on the other end. This ended up being a welcome surprise, because it lets me invert colors in games with the contrast wheel while still retaining the ability to play with normal colors.

What I'm wondering is how this happened. I understand there are backlights that are made to have inverted colors, but from what I understood, they were either inverted or non-inverted without the ability to cycle between the two. What did I do to give my gameboy this ability, and how can I do it again?
I'm sorry if this question seems obvious, but I haven't been able to find answers elsewhere. Any info you guys have would be appreciated!