I can't find an answer on the web so I guess I'll ask

NES is limited to the number of colors it can display. The technique you're talking about is called palette cycling. I'm sure someone more autistic will come along and explain it in more detail soon enough.

>>3839557
Isn't it obvious? Item pickups share the same pallette as megaman.

The NES is limited to using 4 different palettes consisting of 4 colors each at once.
1 is the color of mega man's suit
2 is mega man's face
and the other two are for the enemies currently displayed.
The second palette would make the pickups flesh colored.
Choosing 3 or 4 would also be pretty weird because then the pickups would change color depending on the currently displayed enemies.
The smartest choice would therefore be to make them be the same color as mega man's suit.

>>3839557
>I have a strong hunch it started as a technical thing.

>>>/reddit/didyouknowgaming

>>3839572
Yes but I didn't know exactly why this was done.

>>3839578
Thanks. You mean limited to 4 palettes in terms of active sprites right? The colors used in the level/environment don't play into that?

>>3839591
Autism.

>>3839632
>Thanks. You mean limited to 4 palettes in terms of active sprites right? The colors used in the level/environment don't play into that?
The colors of the game word all have to pull from those 4 palettes too.
And saying their 4 colors is wrong, as the 4th "color" is the transparency bit.
So really, 4 pallets of 3 colors each makes for 12 displayed on screen at once. Thats it.
Every block of 8x8 pixels has to have one of the given color pallets.
Give a huge amount of credit to the artists of the era, since they made so much with such little.

File: Untitled.png (201KB, 1623x927px) Image search: [Google]

201KB, 1623x927px

>>3839669
>>3839578
There is more than that, at least in later games there is but I believe it's the same in previous ones too.

Pic related, top right; the 4 palette of 4 colours used for the game world. On the middle left, the 16*16 (and not 8*8) blocks each limited to one of those pieces.
The enemies or MM don't draw from those pal pieces.

On the bottom right the 2 enemy palette pieces used for the current scroll enemies.

Not pictured: MM's palette pieces. It's 2 more palette pieces which by default should be 0F 2C 11 0F 20 37.

Enemy palettes you can freely change at every scroll.

For BG palettes, not pictured are palette animation. For instance in this pic, the gravity arrow flickers, and that's not a BG animation, that's just the colours of the palette changing. Also,at least from MM3 onwards (if not before, even) they used special effects to be able to change the colours of the bg during a stage at will, and on top of that obviously they change MM's palette on the fly.

So all in all it's not as limited as you make it sound.

To answer OP's question: the E tanks and other items had to use something. If they used enemy palettes, not only their colours would randomly change every time, but honestly it would look weird on a screen with at the same times items and enemies. Can't use BG pallettes either, so that only leaves MM's, but MM's palette colours change depending on the weapon you're carrying, so that affects the items too.