Hi, I have found that changing the paper setting from PLAIN to GLOSSY can make a big difference to the colour/density output of the printer.
I think the printer manufacturers allow for the different absorption rate of the various papers.
For what it's worth I always leave the printer set to PLAIN paper even when using GLOSSY photo paper. At least the colour output remains constant for me that way.
Try using all the different paper settings provided by the printer with the same image (photo or text) while still using PLAIN paper in the printer and you will be able to see differences in the printed images.