so i got the itch to find out once this thread made me look deeper into it. and survey says- dk alphas are confirmed darker than the white. they're basically the same tint as the beige mods, but are grey in color. really cool stuff.
will probably take a pic after work of all the colors next to each other (rf white, pfu white, rf beige, pfu grey, rf-dk lgrey, rf-dk medgrey, rf-10th medgrey) just to show any variances (i don't have any of the dark grey/black caps though).