Rust: type and parameter name annotations are highlited

When coding in Rust, the editor adds parameter names and annotations (i.e. types are inferred but the editor adds them to make the code more explicit). In Cobal2 those annotations are bright yellow, which is really distracting.

For instance, the Dark+ theme greys it out (which makes it less aggressive and helps understand it's secondary information added by the editor):

IntelliJ does an even better job (IMO) since it greys out the font, dimming out the annotations and making them even more subtle.