Generally speaking, we want to select colors from the web palette which are TV safe for our Media Center Hosted HTML applications.  For additional information see TV-Safe Colors in the Media Center Software Development Kit (SDK).  A couple of my favorite design tools are Adobe Illustrator and Photoshop, which make it pretty easy to select these TV safe web colors using the Color Picker.

1) Double-click the fill or stroke color selection box in the toolbox or Color palette.

2) Make sure the Only Web Colors checkbox is checked and then select your colors in the range where no single color in the RGB gamut is less than 51 or greater than 204.

3) Although it's usually not necessary, just to be super safe about the colors chosen you can run the Filter --> Video --> NTSC Colors filter and watch for color shifts in your chosen pallette.