Kester: since this is in DNA, it backwards converts all R into B now, which isn't the bug. On big endian systems (OSX) there engine colors are OK, which indicates the conversion of MCol goes wrong on the engine side, by using some endian-sensative approach. The main confusement is, that the MCol struct isn't in use for read or write in Blender, only for a save in files. The contents of that struct is wrong, yes. See note in vpaint.c top.