test: add test for spec reporter red color output

Add a test in  to verify that
the diagnostic error messages about unmet coverage thresholds
are displayed in red when using the spec reporter.

Fixes: nodejs#55922

test/parallel/test-runner-coverage-thresholds.js

@@ -88,6 +88,24 @@ for (const coverage of coverages) {
     assert(!findCoverageFileForPid(result.pid));
   });
 
+  test(`test failing ${coverage.flag} with red color`, () => {
+    const result = spawnSync(process.execPath, [
+      '--test',
+      '--experimental-test-coverage',
+      `${coverage.flag}=99`,
+      '--test-reporter', 'spec',
+      fixture,
+    ], {
+      env: { ...process.env, FORCE_COLOR: '3' },
+    });
+
+    const stdout = result.stdout.toString();
+    const redColorRegex = /\u001b\[31mℹ Error: \d{2}\.\d{2}% \w+ coverage does not meet threshold of 99%/;
+    assert.match(stdout, redColorRegex, 'Expected red color code not found in diagnostic message');
+    assert.strictEqual(result.status, 1);
+    assert(!findCoverageFileForPid(result.pid));
+  });
+
   test(`test failing ${coverage.flag}`, () => {
     const result = spawnSync(process.execPath, [
       '--test',