I have Madagascar Rosewood on three Private Stocks; the CU24 is very, very dark. The Anniversary model is almost caramel. The Singlecut is kind of dark reddish brown.
There's Brazilian Rosewood on my DGT and have had quite a few with Braz; the color has varied from very dark to lighter; the DGT has streaks of light reddish-brown to very dark.
These rosewoods also sound a bit different from Indian Rosewood. The Madagascar variety is warmer, the Brazilian is a but snappier at the pick attack, so it tends to sound a little brighter.
To be clear, I'm not saying any of these species are 'better', they're just "different', and I like what they do for the tone. ButI like the sound of guitars with rosewood, including Indian Rosewood.
All but open strings touch the frets that are sitting on the wood (I'd guess since the nut touches the fretboard the species might matter there, too), and it matters re: the tone. However, the color doesn't matter at all, I find the different wood shading interesting. It's nice to have a little variety.
We all suffer from different obsessions, I suppose.