feat: enable automatic prefix colors by default

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

@@ -180,4 +180,14 @@ describe('#ACCEPTABLE_CONSOLE_COLORS', () => {
         //     always has more than one entry, which is what we enforce via this test
         expect(PrefixColorSelector.ACCEPTABLE_CONSOLE_COLORS.length).toBeGreaterThan(1);
     });
+
+    it('only includes colors that are visually distinct, semantically neutral, and lightweight', () => {
+        expect(PrefixColorSelector.ACCEPTABLE_CONSOLE_COLORS).toEqual([
+            'cyan',
+            'magenta',
+            'green',
+            'yellow',
+            'blue',
+        ]);
+    });
 });

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.
+     *
+     * Each color is chosen to be visually distinct on both dark and light
+     * terminal backgrounds, without carrying semantic meaning (e.g. red
+     * implies errors) or blending into default text (e.g. white/grey).
+     * Background colors are excluded to keep output lightweight.
+     *
+     * 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'])];
     }
 
     /**