Should I refrigerate canola oil cooking spray?
The answer is no.

Oils are more solid at colder temperatures (how much depends on the oil, 14°F(-10°C) for Canola Oil) While the fridge is not going to reach 'freezing' for the oil it does cause the oil to become more dense and thus harder for it to spray and more likely to clog the nozzle. 

Then there is the propellants, which vary by concentration and brand but are all 'considered safe' but, like the oil itself, condense. As the propellants condense the pressure in the can drops and they become less potent at lower temperatures (see pp.44-48). 



(note: the propellants link above is to an article that gives some good reasons to not use these sprays at all, but that isn't the question you asked. IMHO, while valid reasons to eschew using these sprays 'too much' they are just too darned convenient to not use 'at all')