Majatek has written
Yes, MS Paint for Windows may have that as the pink colour, but trust me - The colour palette that MS Paint has sucks utter shit. Trust me on this one and download+install+use Paint.Net or any other graphics program (such as Photoshop or Paint Shop Pro, etc) that allows for a more in-depth graphics properties and saving process.
Seriously, I bet it's because MS Paint doesn't give two shits about how it saves it's bmp's - In my time I experienced MS Paint using a colour palette less than that of a 32-bit colour mode palette (Some 256 colours) and ended up making my weapon sprite LOOK FUCKING HORRIBLE.
Yeah, because my smooth gradients (from black to white) turned into chunky steps, effectively ruining the look as semi-dark pixels turned completely black.
Stop using MS Paint.
Get a better graphics-editing software.