What DTG printer are you using? We pretreat light & dark color Ts for printing. White Ts do not need pretreat. We have been testing a graphic for printing on color Ts for a customer "Without" pretreat to achieve a different effect. So far all tests have come been positive. Customer loves it. Be sure you are applying enough pretreat also. What brand of pretreat are you using?
You might try using your settings in the software you "Rip" your graphics with. You can "brighten" the graphic, you can also do 2 color passes (on our Rip sw). Hope these ideas help.
Great Dane Graphics has a great book T-shirt Artwork Simplified that goes into at depth the process of brightening images in Photoshop - basically removing the "gray" from the image. Highly recommended reading for DTG users.
A forum community dedicated to T-shirt merchants, professionals and enthusiasts. Come join the discussion about graphics, commerce, dyes, prints, collections, guides, displays, styles, scales, equipment, accessories, reviews, classifieds, and more!