The title pretty much says it all. When you first select a colored pipe and then select the default one again there's an error saying it can't read the color property of the default pipe (which makes sense I think). A simple nil check may resolve this?

Ah yea, the mod in its current form is very much a proof of concept.
If you press the button next to the default color (which will eventually get its own icon, but for now should've been disabled), it'll crash on command :P

When I last touched it, I changed the pipe in your cursor instead of the building after placing. The latter method ruined underground dragging.
I haven't released it because there's just so many ways of transferring it out of your hand besides dropping it back into your inventory (the only method I handled)

I also got into a bit of a slump with modmaking, only to reiginite my desire yesterday with Complex Death Messages, a mod of mine that was left in a not-working state for months.