feat: assign default prefix colors matching turborepo's palette

Change the default prefix color from 'reset' (no color) to 'auto',
so that each command gets a distinct color out of the box.

Set ACCEPTABLE_CONSOLE_COLORS to turborepo's 5-color palette
(cyan, magenta, green, yellow, blue) which cycles on repeat.
This list only controls what 'auto' picks from — manually specified
colors (via --prefix-colors) are unrestricted and accept any valid
Chalk color name, hex value, or modifier.

Author: GermanJablo

docs/cli/prefixing.md

@@ -56,10 +56,10 @@ $ concurrently --prefix '{index}-{pid}' 'echo Hello there' 'echo General Kenobi!
 
 ## Prefix Colors
 
-By default, there are no colors applied to concurrently prefixes, and they just use whatever the terminal's defaults are.
+By default, concurrently automatically assigns colors to each command's prefix, cycling through `cyan`, `magenta`, `green`, `yellow`, and `blue` (the same palette and order used by turborepo).
 
 This can be changed by using the `--prefix-colors`/`-c` flag, which takes a comma-separated list of colors to use.<br/>
-The available values are color names (e.g. `green`, `magenta`, `gray`, etc), a hex value (such as `#23de43`), or `auto`, to automatically select a color.
+The available values are color names (e.g. `green`, `magenta`, `gray`, etc), a hex value (such as `#23de43`), `auto` to automatically select a color, or `reset` to disable coloring.
 
 ```bash
 $ concurrently -c red,blue 'echo Hello there' 'echo General Kenobi!'

lib/defaults.ts

@@ -35,7 +35,7 @@ export const prefix = '';
  * Default prefix color.
  * @see https://www.npmjs.com/package/chalk
  */
-export const prefixColors = 'reset';
+export const prefixColors = 'auto';
 
 /**
  * How many bytes we'll show on the command prefix.

lib/logger.ts

@@ -166,7 +166,8 @@ export class Logger {
                 color = modifiedColor;
             }
         } else {
-            const defaultColor = getChalkPath(this.chalk, defaults.prefixColors) as ChalkInstance;
+            const defaultColor =
+                getChalkPath(this.chalk, defaults.prefixColors) ?? this.chalk.reset;
             color = getChalkPath(this.chalk, command.prefixColor ?? '') ?? defaultColor;
         }
         return color(text);

lib/prefix-color-selector.spec.ts

@@ -181,7 +181,7 @@ describe('#ACCEPTABLE_CONSOLE_COLORS', () => {
         expect(PrefixColorSelector.ACCEPTABLE_CONSOLE_COLORS.length).toBeGreaterThan(1);
     });
 
-    it('uses the same color order as turborepo', () => {
+    it('uses the same colors and order as turborepo', () => {
         expect(PrefixColorSelector.ACCEPTABLE_CONSOLE_COLORS).toEqual([
             'cyan',
             'magenta',

lib/prefix-color-selector.ts

@@ -63,33 +63,19 @@ export class PrefixColorSelector {
         this.colorGenerator = createColorGenerator(normalizedColors);
     }
 
-    /** A list of colors that are readable in a terminal. */
+    /**
+     * Colors used by `auto` selection and default cycling.
+     *
+     * Matches turborepo's palette: cyan, magenta, green, yellow, blue.
+     * These are visually distinct on both dark and light terminal backgrounds
+     * without carrying semantic meaning (unlike red → errors) or blending
+     * into the default text color (unlike white/grey).
+     *
+     * This list does NOT restrict manually specified colors — any valid Chalk
+     * color name, hex value, or modifier can be passed via `--prefix-colors`.
+     */
     public static get ACCEPTABLE_CONSOLE_COLORS() {
-        // Colors picked randomly, can be amended if required
-        return [
-            // Prevent duplicates, in case the list becomes significantly large
-            ...new Set<keyof ChalkInstance>([
-                // Text colors
-                'cyan',
-                'yellow',
-                'greenBright',
-                'blueBright',
-                'magentaBright',
-                'white',
-                'grey',
-                'red',
-
-                // Background colors
-                'bgCyan',
-                'bgYellow',
-                'bgGreenBright',
-                'bgBlueBright',
-                'bgMagenta',
-                'bgWhiteBright',
-                'bgGrey',
-                'bgRed',
-            ]),
-        ];
+        return [...new Set<keyof ChalkInstance>(['cyan', 'magenta', 'green', 'yellow', 'blue'])];
     }
 
     /**