This project depends on the 1.12 version of Chameleon as stated by evaluationDependsOn(":..:Chameleon-${minecraft_base_version}")

The issue is, :..: is not a valid path specifier, nor a valid name afaik.
This also seems to be including the Chameleon library as a sub-project rather than a library.
If this is intended, I would propose adding Chameleon as a git submodule instead.
If not, a simple way of loading it from a libs/ folder would suffice as it would give a clear indication it looks for the library there.

You'll need to be more clear about how you're using the gradle script. This scheme has been working well for me for standard gradle build, and for setting up an IntelliJ project with both the mod and Chameleon included as modules. That makes development much more convenient for me, with the pre-requisite that both projects are first checked out as directory peers.

Edit: Ok wow, Gradle is very weird with its import system, : is the name deliminator, .. path specifier, and then : again.

Issue is, I had cloned Chemeleon inside GardenStuff and tried loading it from ./Chameleon-1.12 while forge would need it to be :.:Chameleon-1.12 which imo is just awkward.