I'd recommend asking Seven to send you color (paint) swatches. I really don't think that you'll be able to see the results that you want by using markers or colored pencils. A semblance, yes, but reality, probably not. Although as long as you know the colors are going to be a bit off playing with pencils or markers should give you a general idea.
Also - make sure to look at the color swatches in daylight, on both sunny and cloudy days.
--- Denise