This is absolutely the case. The black that is usually printed by ink jet printers on paper is about 75% cyan, 70% magenta, 70% yellow, and 90% black. Those percentages are in relation to the maximum output per head. If you are running all your printing through some form of RIP software where you can directly control ink volume, you’ll very quickly see that using only black ink gives you very poor color.

And, fun fact, this is true with black and white photos as well. If you force your printer to use only black ink, you’ll get washed out images with poor contrast. I found this out because the printer and RIP that I operate will default to black ink only when an image is specified as greyscale, and I was getting terrible images. Saving the images in RGB (note: RGB ends up printing with a slightly wider gamut than CMYK) completely solved the issue.