Surface Transparency

Aside from specifying the transparent color, you need to explicitly enable the AlphaTesting render state as described here. This will tell D3D not to render the transparent pixels of your texture. Don't forget to disable alphatesting when you're done with your HUD rendering, to save some performance and prevent unexpected transparency effects in the rest of your game.

If you need partial transparency ('see-through') you might want to look into alpha blending. This is a bit more complex as it brings in the need to perform some depthsorting manually (objects behind transparent objects need to be rendered first), but that shouldn't be too hard to do for a HUD.

Edit: if you're using D3DX sprites to render your hud, you should either pass in D3DXSPRITE_ALPHABLEND to the Begin method to tell the sprite to use alphablending OR you can pass in D3DXSPRITE_DONOTMODIFY_RENDERSTATE to tell the sprite to respect the renderstates you set. Otherwise the sprite will happily modify the renderstates to fit it's own needs.

Hope this helps :)

Okay. I've been using offScreen surfaces to make the interface for the game, but all I keep hearing about is using sprites and such. I don't know how to do that yet, so I guess I'll start experimenting with it.

Thanks for the help!