What do the colors of resistor bodies mean?

I've seen a few manufacturers that make their high precision metal film resistors blue and their generic paper/carbon ones pale brown, but I'd guess it's not a universal thing...it's like when Walkers (Lays) crisps messed around with the colour flavour combos, everyone had to relearn cheese & onion and salt & vinegar grrrr!

It's up to the manufacturer, it doesn't have any relevance to the properties of the device.

You haven't seen different colors until you've seen inside a scope, or at least an old one.

HP 54501A

From a HP 54501A.

You can take a guess at what the colors mean, but without knowing the manufacturers it is difficult, nigh impossible. In this example suspect the green ones are precision (probably ±0.1%), while the pink and blue ones have larger tolerance, due to the relative quantities of them.