Colors can look very different on fabric than they do on your computer monitor. Light goes through and bounces off of color on fabric. Colored light comes out of a screen. Fabric has gossamer qualities: it's 3-D and it folds and drapes, but screens don't. Fundamentally different!
Our digital printers and inks often print saturated colors and true blacks lighter than you might expect. You may need to test different saturation levels or modify your design.
Your chosen colors might "shift" to colors you weren't expecting if they are out-of-gamut for our printers.
Because our fabrics have different white points, colors will shift brighter or darker based on your fabric choice.
Test swatches are cheap and fast.
There's simply no substitute for determining how a design will print than having the design printed!