Creative Progress Maps come on either museum-quality print or satin-finish canvas. So when it comes to coloring, your options are two very different materials. Ink from the same pen will not look the same on print as it does on canvas.
Generally speaking, it looks darker on the print. You can see in the photo above that the Sharpie pen in Berry looks quite different on canvas (on the left) than it does on print (on the right). That's why I offer a Color Tester for prints.
To test colors for canvas, I recommend just using the back of the canvas. As the canvas frames are 1.5 inches wide, you'll have a decent amount of space to test different colors, even on the smallest canvas size. You'll start to notice that some pens look richer on the canvas (ProMarkers), while others look more translucent (Copic). And, if that's not enough detail for ya, it also varies on the depth of the shade itself—dark colors vs. pastels.
My best advice for those folk who like to get into this level of detail is to test before you starting coloring your map. It's easiest to do this at a store where you can test lots of colors and brands.
My favorite store is the Art Supply Warehouse in Westminster, CA. I dig the art stores because they tend to have a much wider selection and you can buy individual pens. I also think it's a win when you can support local art stores.
Though there are also some great art supply chains with locations through the country, like Dick Blick.