Mention 'color' feature in README

Mention the existence of the 'color' feature in the README, to make
users aware of it.

README.md

@@ -30,7 +30,7 @@ let _ = env_logger::builder().is_test(true).try_init();
 in **each and every** test.
 
 Similarly, `tracing` based solutions require a subscriber to be
-registered that writes events/spans to the console.
+registered that writes events/spans to the terminal.
 
 This crate takes care of this per-test initialization in an intuitive
 way.
@@ -103,15 +103,18 @@ on what the events mean.
 
 #### Features
 
-The crate comes with two features:
+The crate comes with two features pertaining "backend" initialization:
 - `log`, enabled by default, controls initialization for the `log`
   crate.
 - `trace`, disabled by default, controls initialization for the
   `tracing` crate.
 
 Depending on what backend the crate-under-test (and its dependencies)
 use, the respective feature should be enabled to make messages that are
-emitted by the test manifest on the console.
+emitted by the test manifest on the terminal.
+
+On top of that, the `color` feature (enabled by default) controls
+whether to color output by default.
 
 #### MSRV Policy
 This crate adheres to Cargo's [semantic versioning rules][cargo-semver].