Sky Texture Are Black And Purple Squares

I have searched and searched and searched. There seems to be no answer! I have recently downloaded FreeSpace Revolution and its fix, but the sky is still black and purple squares! I’m trying to find a sky texture, but I come up empty!
Please, help!

Thank you.

What source games do you have? Some sky textures are from CS:S

I have Half-Life 2 (with Lost Coast).

You’ll probably need to get CS:S to see the sky texture

But I don’t want to buy it. Isn’t a way to just get the texture alone?