The elephant to the right is all one color, but it appears different on the different background colors.
Here’s another example. The small squares in the center of the larger squares to the left are actually the same color. Keep in mind that the item color that you choose may change the appearance of your printed design at a distance or in different lighting.
CONSIDER THE UNDERBASE
What’s an underbase? It’s a thin layer of white ink printed under solid colors to make them brighter and more visible on a dark shirt.