My bike came with the appropriate rear light, as have many others I've seen.
At the point of sale I was was issued an ugly sticker that was supposed to be attached permanently to the frame according to the guv... it wasn't yellow it was offwhite and composed with some sort of metallic base... but mine somehow got lost, and was never affixed.
There is supposed to be an offence and penalty under the ORegs of the Highway Traffic Act here in Ontario for not attaching it, but I couldn't locate it and I am a Provincial Offences Act Instructor... if I can't find the appropriate charge I will bet my left testicle that there are very few other LE guys who can, or even care to!
I can see the reasoning for the yellow one though... if you change the speedo it is possible that some dude who may be less than honest could rapidly reduce many miles on an otherwise tired bike offered for sale.