So you get to pick the colors?? Of course some colors like Sunoco would be known. I was guessing mid 50's, the Buick jumped out to me, not to mention the 26.9 gas price.
Yep, I have to interpret the colors based on whatever I can find for the period the photo was taken.
I have also learned to interpret colors based on their shades of gray tones by using known references like the colors of trees, wood, concrete and asphalt.