Clashing colors is no good, but using the color of your garment to make your design that much better is a GREAT IDEA!
I developed some some real quick tips to think about on how to enhance your tee design using the color of the shirt.
1) You must start by understanding who your logo is targeting. If the audience is at a distance you want to make sure to increase the contrast between the garment and the color.
2) Low visibility is the result of colors close in value, which can be nice if the target is close by.
3) If your garment contains the same color as your shirt, you can use the shirt as a negative space in your image.
4) If you plan your color schemes first, you will avoid missing small details such as listed above.
5) Always create mock ups or have The Printory create them to your specs before you approve your printing.