I never would've thought about splitting the RGB values, much less switching them and even less likely to substract 5 from them. xD
The 1-8 rollers won't be touched right now, since it seems that the ones from the GBA port have the exact same palette as the ones from the SNES game, so that's one more down.
As for the spinning platforms in 2-4, they are handled differently in the GBA port it seems.
They had some sort of texture-like colours in the SNES one, but they seem to be a plain colour in the GBA version.
They also seem to be fine though.
I think those were pretty much all the 3D objects in the game.
Right now, I am focusing on trying to figure out the remaining gradients/colours for the stages 2-6, 3-1 and 6-1.
Here's an example for 3-1:
As you can see the colours are not exactly right, and you can see a line that divides what seems to be the blue colour of the background clouds with another shade of blue.
Also the sky seems to be lighter than the original SNES counterpart.
The colours seem to change on the fly between 0x937F and 0x997F (this includes 93, 94, 95, 96, 97, 98 and 99), with the colour 0xD172 I set sometimes getting in there.
(You can watch this in the Memory Viewer -> Palette)
The values in RGB are 192831 for 0x937F and up to 252831 for 0x997F.
I converted them to HEX, subtracted 0x05 for each colour and got 13171A for 0x937F and 19171A for 0x997F.
Switched they should be 1A 17 13 and 1A 17 19. Search for those and changed them to 1C 16 11 (which should be 0xD172) but no luck so far.