Hi William. You don't say which sim this is for or which version of FSDS you're using. You can either use transparent textures or create the windows from transparent parts. The latter is my preferred method where practical. The colour/opacity/transparency value can be assigned from FSDS Part Properties. FSDS also has a Create Transparent Texture feature.

PS. You can also use BMP2000 or DXTBmp to create textures in one of the transparent formats compatible with the particular sim.

OK. This should not be a problem once you figure it out. I suggest trying transparent textures to start with. Use the FSDS onboard File/Create Transparent Texture feature to set the transparency of the window colour of the texture. This should be a shade not used elsewhere on the texture. Then go to Part Properties of the appropriate parts & check the Uses Transparent Textures option.

Please try it & tell me how you get on.