nctrnOWL, to my understanding, the bottom palettes are the sprites with their RGB channel values in multiples of 8 (8, 16, 24, 32, 40, 48, 56, 64, etc., up to 248), while the top palettes use the same values, but with a 1 added every four values (8, 16, 24, 33, 41, 49, 57, 66, etc., up to 255). This is because the palettes for the sprites are stored in a 15-bit color format, which only allows 31 values per RGB channel (totaling up to 32,768 unique colors), while most imaging software uses a 24-bit color format that allows 255 values per RGB channel (totaling up to 16,777,216 unique colors). In other words, this sheet uses two approximations based on the 15-bit color format.

I don't think you understand the meaning of "objectively"

Also does either of u know which are the 'original' sprites seeing as how the sheet has 2 variants?

@Doc: Yeah ur right I can do it myself :)

Anyways, any program that uses transparency probably has a magic wand tool, just use that with a tolerance of zero and erase the blue with it. Or with Paint, set the blue as the secondary color with "make transparent selection" on (last part applies for newer versions only). Paint.net can do similar things, but INEXPLICABLY requires making a new layer.

Paint is objectively much better to use for simple graphics, as a lot of steps required for other programs are simply redundant and time-wasting for said simpler graphics (ie bounding boxes, creating new layers, et cetera).

@RTB: Do u by any chance have the sheet with a clear background?

@nctrnOWL: Two reasons:
1. People still using Paint for whatever reason will be able to use this sheet without the transparency being completely black and interfering with the sprite colours (though none are completely black / R0,G0,B0 on this sheet, it could apply to others).
2. Having the sprite sheet be opaque for cases like this (basically things with 1-bit transparency) takes up less space -- 1,058,187 bytes instead of 995,049 bytes. Not a whole lot of difference, but still one regardless.

@RTB: Why the blue background instead of a clear one?