Canon S400 Reference Manual page 143

Colours not clear
Check 1
BJ Cartridge and media correct for the print job?
For printing photographs, illustrations, use of High Resolution Paper,
Glossy Photo Paper or High Gloss Photo Film is recommended. These
media provide better colour reproduction and brighter colours than plain
paper.
For best results, use the Color BJ Cartridge BC-34e Photo.
For printing colour graphs, charts with text, use the Color BJ Cartridge BC-
33e to print reports and research papers.
A clogged or worn BJ Cartridge may also cause printing problems. Print a
nozzle check pattern and check the printed patterns.
Printing a Nozzle Check Pattern
Troubleshooting - Printout is Unsatisfactory 143