So about the Collossi Rebicantus?

[Cilia]

The specific term is "Rubricatus," which literally just means "red" in Latin. So it's a red Magitek Colossus.

In fiction, red things tend to have a higher performance (i.e. Char Aznable's Red Comet from Gundam, which literally just looks like a standard issue Zaku painted red but with three times the speed). The color just denotes that it's better than standard Magitek Colossi.

See, that's why I went to all the effort of beating Memory Varis EX and getting enough Skybuilder's Scrips to get the Ruby Red dye - now I have a red GNB coat, which automatically makes it 100% cooler.