On a Dutch forum there is an ongoing discussion on this.
Click!
Some people even claim to see colors with 7x50 binos from downtown Antwerp which is obviously not true.
Others even claim to see red / purplish colors. I think that exit pupil is the most important factor as that determines surface brightness. A set of 7x50 binos have a better surface brightness (50/7=7.1mm) than a 75x eyepiece on a 40cm Dobson (400/75=5.3mm), but, obviously, the Dobson show much more detail as it is zoomed in more than 10 times with only slightly lower surface brightness. But the higher surface brightness would allow to see colors in bright nebulas like the Orion nebula, but also eta Carinae or the Tarantula, even with a small scope (10cm or less). But a pitch dark location is an absolute requirement so, Sydneysiders, Melbournians, sorry. I never tried it, did somebody try this with a small aperture ?
During my upcoming South Africa trip I will try it definitely.