"In space, no one can see you well."
Face it, space is a dark place. The bright, sometimes gaudy colors of studio starship models never make in to the screen. The image below shows the difference between the studio colors (on the right) and a conservative color adjustment (left) to make space colors for this Ambassador class starship.
By using a paint program, I've adjusted the colors to the reduced saturation and luminance values shown (Sat -70%; Lum -30%), approximating the appearance of the ship onscreen.
You can use a scanner or digital camera as a means to test paint mixes to see how closely they match the colors a model needs to be. In the image above, I've picked out three of the adjusted colors and labeled their approximate R-G-B color values. Next make a range of paint mixes -- e.g., dark blue-grays to match the nacelle detail color -- paint a swatch of each mix on plastic, then scan the swatches (after they've dried!) and determine the RGB value of each swatch. Find what's close, make more swatches, and eventually you have the One Perfect And True Color!
Unless the space light changes. I mean, my evil twin wants to paint up Enterprise and Reliant kits in pinks, blues and mauves and call it the Mutara Nebula battle scene. Evil!! Eeee-vil!!