It's not a bug, it's a design by you :)
Scene color is, well, the color of the pixels behind the object, which means it will look invisible unless modified, and in this case, you aren't modifying it (yet)

It's just the type of thing that's not really fit for being done on a shader level :)
Generating textures from SF is somewhat outside the scope of what SF does, but there might be some node-to-texture export thing at some point

For two colors, you can simply plug in two colors in A and B, and the pattern you want to put the gradient on in T :)

For more than 2 colors, you're usually better off using a texture as a color map, like this:

This is a silly issue, but should be fixable. Looking into it :)

Edit: Fixed in Beta 0.24

This is a silly issue, but should be fixable. Looking into it :)

Edit: Fixed in 0.24

Strange, free shouldn't support it yeah. Closing this anyhow, as the deferred compatibility has been reported multiple times :)

Are you on deferred or forward rendering?