yugas and colours

[Dominic Goodall]

Dear all,

Can anybody tell me whether the notion that Vi.s.nu changes colour in  
each yuga predates the Bhaagavatapuraa.na?

BhP_10.08.013/1 aasan var.naas trayo hy asya g.rh.nato 'nuyuga.m tanuu.h
BhP_10.08.013/3 "suklo raktas tathaa piita idaanii.m k.r.s.nataa.m  
gata.h

I find it in a few passages excluded from the critical text of the  
Mahaabhaarata, e.g.

13*0002_01 ya.h "svetatvam upaagata.h k.rtayuge tretaayuge raktataa.m
13*0002_02 yugme ya.h kapila.h kalau sa bhagavaan k.r.s.natvam  
abhyaagata.h

Does anybody know of any demonstrably early references?

Dominic Goodall