Yep, this is a far cry from going out there in a white T-shirt. It's probably very good camouflage from the deer's perspective. And no, I'm not saying a deer can't be killed with a white T-shirt. Lot's of deer could probably be killed with a white tyvek suit on. I'm just saying if you are trying to be undetected on your walk or don't want a deer to see you getting in your pack for something then white is probably the worst color. Sometimes the small details make all the difference in the world, other times they don't matter at all.
I told him it would never work....Whatever that means, your picture has little to do with white. If you want an apples to apples comparison, there is literally an apples to apples comparison you can read about. There was a deer vision study done with yellow and red apples and it produced some strong conclusions.
Red plaid was a favorite of northeastern hunters for many decades and worked fine even when hunting from the ground because red doesn't look red to deer. So red doesn't move the bar for me.
Because deer eyes are engineered to have a primary acuity at ground level, you can likely get away with colors that stand out to them when elevated if you don't provide them with other signs of your presence.
I would paint or dye (if the material will accept it) the pack myself.