There are two main types of transfer papers: light and dark transfer papers. A light transfer paper has a polymer that when heated up, turns clear. When you print on a light transfer paper, you mirror image your design so that when you flip the paper on to your garment... it looks straight after your press / peel the paper backing on the transfer paper. A dark transfer paper has a white backing that will separate from the paper backing. When you print on a dark transfer paper, you will print the design regularly (not mirror image) and then peel the white backing from the transfer paper. You then set the white backing on the garment straight up and will typically use a cover sheet to protect the top of the transfer paper while you press it. The white backing makes the feel of a dark transfer paper heavier because it has to block out the color of the garment. The inks you will use are transparent. So it you try to print a blonde caucasian girl on a light transfer paper and apply it to a pink shirt... she will look like she has a sunburn and has pink hair. The same principles apply to dtg printing / screen printing and whether to print a white underbase or not.
Hope this helps.
Mark
Hope this helps.
Mark