that's because the media you are using. If you use paper, look at the ink it can eat... if its little (under 250%), the colors will be faded. So first... try to print a red and black thing in a vinyl (every vinyl I know, can handle lots of ink). If the colors are not faded, its just a media thing (its very usual, dont worry about that... you just need to find the best media for your plotter from your dealers). sorry for my english!