Its not uncommon to paint a boat two different colors but its always been different colors on the top and bottom.  In 33 years I've never painted one differnt colors from side to side!  Of course now that I had one in the shop to do, all of a sudden I get another one!  Two in the same year, what were the chances.
The yellow and red is a 1958 Old Town Otca.  The red and green is a 1963 Old Town 50lb model. 
The 50lb model is an interesting bit of Old Town Canoe Co. marketing.  The name of the boat is the "50lb model".  That does not mean the boat weighs 50 lbs, its just that is the name of the boat.  They produced 50lb modles in various lengths from 17 to 12 feet long and of course they all weighed different amounts, some over 50lbs and some under, but I'm sure one of them did weigh 50 lbs.  The models were built a bit lighter than the standard canoes so it was intended to be a light weight model and purhaps the first one they did weighed 50 lbs.  I have not weighed this canoe yet but it will be interesting to see what it turns out to be!