All right, maybe these questions have already been asked before, but I have not found any records in this board's message database confirming this, so here they go...

I am aware of the fact that writes to $3f00 and $3f10 are ultimately mirrored to $3f00. Also, the same color written to those areas would be stored in $3f04, $3f08, $3f0c, $3f14, $3f18, and $3f1c. My question is, would colors stored in these latter areas (excluding $3f00 and $3f10) be considered as transparent colors, or would they be drawn on the screen in case some tile referenced them? Also, are writes to such areas completely ignored?

Thanks in advance.

hydesprojects.cjb.net

well writes to 3f00,04,08,0c,10,14,18,1c should be same - just to make sure you don't get a unexpected background colour
the 1st 4 reflect the background colour, the next 4 are transparent in sprite
so you get 12 colours for tiles, 12 for sprites and a background colour

3F00,04,08,0C,10,14,18,1C should all be considered transparent. Writing to 3F00/10 sets the background color. Writing to 04,08,0C,14,18,1C has no effect.

For emulation purposes, it's often suggested that 3F00/10 writes are mirrored to 04,08,0C,14,18,1C. This can produce the same effect as above, but technically it's incorrect.

So if I understand this correctly 3f00 and 3f10 are mirrors of eachother and 3f04, 3f08, 3f0c, 3f14, 3f18, and 3f1c are not used. Is this right?

yep.. that's about the gist of it.