With mobile network operators using more and more radio systems (GSM, UMTS and LTE) simultaneous and on many different frequency bands, it's getting a bit difficult with traditional network coverage maps to find out where what kind of mobile device can be used. Some network operators have therefore now begun to diversify their maps with options to show different technologies and different frequency bands different colors.
Two interesting examples:
Elisa from Finland shows GSM, UMTS 900 and UMTS 2100 and LTE (1800???) coverage and dual carrier operation in separate colors
T-Mobile Germany that shows GSM, UMTS, LTE 800 and LTE 1800 in different colors (especially for devices that are not LTE 800 capable...)
In both cases, GSM coverage is still wider than the combined UMTS and LTE coverage. Such maps are also interesting to deduct what kind of network strategy the operator follows.