The red switch, if the same as the 190e i have is for the Electromagnetic fan, the one behind the rad in the engine bay. This one activates at about 100 degrees and shuts off at about 90 degrees. Allow a variance for an older switch.
The blue one (which i havent got) would be for the aux fans. I think these have a dual purpose, they come on when the aircon is activated, plus they also come on if the standard fan isnt cooling enough, ie on a particularly hot day. I would imagine they should come on at about 105-110 degrees and shut off at 100.