When ordering custom printed labels be aware that spot ink colors will appear differently when printed on a gloss versus a litho (matte finish) label stock. The variance can be significant depending on the color you select. This holds true, as well, for a coated (glossy) paper stock versus an uncoated (matte finish) paper stock.
If you are switching from a gloss label stock to a litho or vice versa, you should compare color swatches for both coated and uncoated stock for the spot ink colors you intend to use.
You can also make a comparison by using the coated and uncoated color pallets that come with the more robust computer graphics programs. Although there is likely to be a variance in the appearance of the colors on the computer screen versus the printed colors, at least you will have an idea of the relative difference in the appearance of your colors on coated and uncoated stock.
Once you have compared the difference in appearance of your ink colors on gloss and litho label stocks, make adjustments, if any, to the label colors you specify in your order to achieve the best match.