It has already been done, no need to worry.
The characters that go DT are:
DMC1: Dante - Sparda
Dante has 3 DT. One blue with Alastor, one orange/red with Ifrit and one crimson in the last battle, his true DT.
Sparda has 3 DTs as well, but in this kind colour is the only difference, while in Dante's DT there are changes in the appearance as well. The colours are Blue - Orange - Red.
DMC2: Dante - Lucia - Trish
Dante has 2 DTs. One Red&Black and the Special/Super/Sparda DT in which the colours are about the same but there is more black than red.
Lucia - Blue.
Trish - Black.
DMC3: Dante - DMC1 Dante - Sparda - Vergil - DMC1 Vergil
Dante has as many DTs as his Devil Arms. But the colour to all is red.
In DMC1 clothes he has always the same DT and the same colour, orange/red.
Sparda the same.
Vergil the same with Dante, but his colour is blue.
And DMC1 Vergil, the same with DMC1 Dante but the colour is Dark Blue.
Hope that explained right^_^