look at the sourcecode ?

I did, but I can't read C, so it wasn't much help... 😒

1#define SCALERNAME              RGB2x
2#define SCALERWIDTH             2
3#define SCALERHEIGHT    2
4#define SCALERFUNC                                              \
5        line0[0]=P & redMask;                           \
6        line0[1]=P & greenMask;                 \
7        line1[0]=P & blueMask;                          \
8        line1[1]=P;

So it is just like normal2x (e.g put the same value in 4 pixels), but here 3 of the pixels only show the component in a certain colour. A bit like how an old TV works.

So one pixels shows how much red there is, one how much green and one how much blue.
and one shows the original

ah, I see. Thanks for the explanation! 😀

I think RGB3x should be this way:
GWB
RBW
WRG
Cause right now green pixeles are next to each other actually making one 2x larger pixel.

Or even:
GRB
RBG
BRG
as in 3x all pixels can be used unlike in 2x where there is one pixel that cannot be neither R nor G nor B (unless you would like to reduce its intensity by half).

this the current

1        line0[0]=P;                                                     \
2        line0[1]=P & greenMask;                         \
3        line0[2]=P & blueMask;                          \
4        line1[0]=P & blueMask;                          \
5        line1[1]=P;                                                     \
6        line1[2]=P & redMask;                           \
7        line2[0]=P & redMask;                           \
8        line2[1]=P & greenMask;                         \
9        line2[2]=P;

Yes i know.
I looked at the source and that's why i have posted my suggestions.

Harekiet's looks quite nice, also don't see any problem with 2x1 green blocks.

Actually after rethinking my both suggestions were worse.

But this one is better:
WRG
RBW
WGB

with Harekiet's version if you make a green line like this / green pixels will have a gap of two subpixels width. While such a green line \ has no gap at all. You can also see it with letters for example: O, D U.

With my suggestion there will never be such a large gap with every colour and every direction.

This one will be more Harekiet's style but also with no gap:
WGB
GRW
WBR

(EDITED)