Depands on when you want to model it from. CH-46 Sea Knight has been around since the mid-1960s and has seen many, many different color schemes and is used by multiple different nations. Here is a link to a bunch (over 2,400) images in all sorts of colors and markings.
http://images.google.com/images?q=Sea+Knight&hl=en
Some interior pics as well. For interior colors, cabin is shades of medium grey with either red or green webbing as seats. Cockpit is grey as well on early versions, with black details such as gauges and instruments. Later (late '70s to early '80s), when night vision goggles came into use, cockpits were painted all flat black so they did not interfere with the goggles.
Here are a couple great models of modern CH-46s done by Joe "Mother" Szczygiel:
http://www.hkngallery.org.uk/hkngallery.nsf/9e7858703c56bfb280256b960044cd7b/063f4460e3c7ff7380256fef00164a82!OpenDocument
http://www.hkngallery.org.uk/hkngallery.nsf/9e7858703c56bfb280256b960044cd7b/dc9d54910148066b80257028006474b5!OpenDocument
Hope that helps and gives you some ideas.
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