Another view said "Forget making 1red 1 yellow ,simply make all RED - turning it into 4Way stop much safer for everyone. "
As I previously stated, the yellow/red has to do with where provincial/municipal infrastructure interacts. The highway (18th Street, parts of 1st Street, most of Victoria Ave) will ALWAYS have the yellow because they're provincial trunk highways, and all the intersecting streets will be red. The only exception would be 1st/18th & 18th/Vic, as they are both highways.
Usually when it's municipal meets municipal, it will be all red as far as I can tell.