How to Match PMS uncoated to a PMS coated color

Part of the problem is you are printing on cardboard which soaks up the ink leaving not much reflectance ( that's why it is dull ).  In order for the ink to pop, you may have to print with a White underprint and a varnish overprint. Pantone swatches are printed on White paper, coated and uncoated and matte.  It's almost impossible to achieve the reflectance of ink on White paper with shipping containers ( brown cardboard ).  Even a Pantone 300 option will have the same problem.  Just not as bad.

Similarly, but with a slightly different result, to Printer_Rick's way of doing it, you could use Illustrator. You would create a shape with Solid Coated 285 as the fill. Then go to Edit > Edit Colors > Recolor Artwork > Color Books > PANTONE+ Solid Uncoated. It gives the close approximation as PANTONE 3005 U. Both Photoshop's result and Illustrator's result are very close to the original Solid Coated 285, but Photoshop's result of 300 U is a little darker than the original 285 C and Illustrator's result of 3005 U is a little lighter than the original 285 C. It's almost as if the original 285 C color is smack dab in the middle of the two colors as far as brightness. So, maybe you should use both methods and pick which you prefer -- the lighter or darker one -- for your needs, depending on the background color.

There is a trick I use in Photoshop sometimes. Click on the Color Picker in the Tools. In Color Libraries, go to Solid Coated 285. Then change the Library to Solid Uncoated.

The result is PMS 300 U. It is not a great match by any means, but it is probably the closest match Solid Uncoated has to offer.

Uncoated paper has a tremendous effect on ink appearance, that is why the 285U is so washed out compared to 285C.

Every Pantone color has a Lab definition, which you can see in the Photoshop libraries. What Photoshop is doing is seeing what color in the Uncoated library has the closest Lab equivalent to 285C. 285C is L46, a-4, b-58. 300 U is L43, a-8, b-49.

The L values is fairly close, but the other values present problems. A in Lab moves from green(-) to magenta (+), with 0 being neutral (neither green nor magenta). Because a in 300U is -8, and in 285C the a is -4, 300U is moving just a little more towards green (not a lot, but a little)

The b value is a bigger problem. B in Lab goes from blue(-) to yellow(+), with 0 being neutral. The b value in 285C is -58, while the b in 300U is -49. This means that 300U is significantly "grayer" (less colorful) than 285C. But again, 300U may be your best bet on uncoated paper.

Your other option is to look through an Pantone Uncoated swatch book and choose a color that you think is best for your purposes.

Hope this helps.