Try this

test/jest-light-runner/package.json

@@ -13,6 +13,7 @@
     "jest-each": "^27.3.1",
     "jest-mock": "^27.3.0",
     "jest-snapshot": "^27.3.1",
-    "piscina": "^3.1.0"
+    "piscina": "^3.1.0",
+    "supports-color": "^9.0.2"
   }
 }

test/jest-light-runner/src/index.js

@@ -2,6 +2,8 @@ import { Piscina } from "piscina";
 import { MessageChannel } from "worker_threads";
 import os from "os";
 
+import supportsColor from "supports-color";
+
 import chalk from "chalk";
 import tty from "tty";
 
@@ -18,11 +20,14 @@ console.log(
 const piscina = new Piscina({
   filename: new URL("./worker-runner.js", import.meta.url).href,
   maxThreads: os.cpus().length / 2,
-  env: process.env,
+  env: {
+    // Workers don't have a tty; we whant them to inherit
+    // the color support level from the main thread.
+    FORCE_COLOR: supportsColor.stdout.level,
+    ...process.env,
+  },
 });
 
-const isTTY = process.stdout.isTTY;
-
 export default class LightRunner {
   /**
    * @param {Array<Test>} tests
@@ -39,7 +44,7 @@ export default class LightRunner {
         mc.port2.unref();
 
         return piscina
-          .run({ test, port: mc.port1, isTTY }, { transferList: [mc.port1] })
+          .run({ test, port: mc.port1 }, { transferList: [mc.port1] })
           .then(
             result => onResult(test, result),
             error => onFailure(test, error)

test/jest-light-runner/src/worker-runner.js

@@ -29,13 +29,9 @@ import "./global-setup.js";
   };
 }
 
-export default async function ({ test, port, isTTY }) {
+export default async function ({ test, port }) {
   port.postMessage("start");
 
-  // worker_threads always report isTTY as false;
-  // inherit it from the main thread
-  process.stdout.isTTY = isTTY;
-
   const stats = { passes: 0, failures: 0, pending: 0 };
   const results = [];
   const { tests, hasFocusedTests } = await loadTests(test.path);

yarn.lock

@@ -1014,6 +1014,7 @@ __metadata:
     jest-mock: ^27.3.0
     jest-snapshot: ^27.3.1
     piscina: ^3.1.0
+    supports-color: ^9.0.2
   languageName: unknown
   linkType: soft
 
@@ -9272,6 +9273,13 @@ fsevents@^1.2.7:
   languageName: node
   linkType: hard
 
+"has-flag@npm:^5.0.0":
+  version: 5.0.1
+  resolution: "has-flag@npm:5.0.1"
+  checksum: e0a151db8e43b528258c4269c23224c691b42c1f5168f6d88b61c3f9398ef16d44226a78a0596642da55851cf306a8afe57d6936d4d69a24b66fd10de1373da8
+  languageName: node
+  linkType: hard
+
 "has-symbols@npm:^1.0.1, has-symbols@npm:^1.0.2":
   version: 1.0.2
   resolution: "has-symbols@npm:1.0.2"
@@ -14553,6 +14561,15 @@ fsevents@^1.2.7:
   languageName: node
   linkType: hard
 
+"supports-color@npm:^9.0.2":
+  version: 9.0.2
+  resolution: "supports-color@npm:9.0.2"
+  dependencies:
+    has-flag: ^5.0.0
+  checksum: 690c21f61945a1ebab61fbc9dc861672b1d9678359ce75312b8b7ecb873f37f2ed2df56daa4ef4265300bea2e51f8285831ffb0a190ac46aaeed1d5b44fd51fe
+  languageName: node
+  linkType: hard
+
 "supports-hyperlinks@npm:^2.0.0":
   version: 2.1.0
   resolution: "supports-hyperlinks@npm:2.1.0"