Yeah, I think red too.
I have a couple 152 and 153 guns in yellow boxes but they all have some sort of late ship excuse for them, like S marked Seconds, U marked Used, and the batch of misfits that for one reason or another didn't ship until a 2009 warehouse cleanout but those have orange barcoded labels.
My earliest yellow box that I am absolutely certain of being period correct was a gun my dad bought new, a GA-36T Big Grip target model and it is 154-86xxx. The highest SN red boxes I have that I have that I suspect are correct are for a NIB consec pair of GA-34 guns w/shippers at 154-93xxx. So as with a lot of Ruger things, there are higher number guns with the older accessory/part and vice-versa. But by and large, my sense is that the red to yellow changeover was in that upper range of the 154 prefix.