Change Text Field Selection Color in Flutter

I’d like to create a text field in Flutter where, when I select a portion of the text and press a button, only the selected part changes its color, for example, to red. Moreover, if another section of the text is selected and its color changes, the previous text’s style should be preserved.

My goal is to modify the colors of different portions of text within a text field in Flutter. What steps should I follow to achieve this?

My code is this but it can’t be editable :

import 'dart:math';
import 'package:flutter/material.dart';

void main() => runApp(const MyApp());

class MyApp extends StatelessWidget {
  const MyApp({super.key});
  @override
  Widget build(BuildContext context) => const MaterialApp(home: MyHomePage());
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});
  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  static const _text = 'Lorem ipsum dolor sit amet, '
      'consectetur adipiscing elit, '
      'sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. '
      'Ut enim ad minim veniam, '
      'quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. '
      'Duis aute irure dolor in reprehenderit '
      'in voluptate velit esse cillum dolore eu fugiat nulla pariatur. '
      'Excepteur sint occaecat cupidatat non proident, '
      'sunt in culpa qui officia deserunt mollit anim id est laborum.';
  final List<TextStyle> _style = List.filled(_text.length, const TextStyle());
  (int startIndex, int endIndex) _selection = (0, 0);

  Widget get highlightedText {
    final List<TextSpan> children = [];
    String currentText = '';
    late TextStyle currentStyle;

    for (int i = 0; i < _text.length; i++) {
      if (currentText.isEmpty) {
        currentText = _text[i];
        currentStyle = _style[i];
      } else {
        currentText += _text[i];
        if (i + 1 == _text.length || _style[i + 1] != currentStyle) {
          children.add(TextSpan(text: currentText, style: currentStyle));
          currentText = '';
        }
      }
    }

    return SelectableText.rich(
      TextSpan(children: children),
      onSelectionChanged: (selection, cause) {
        final (base, extent) = (selection.baseOffset, selection.extentOffset);
        _selection = (min(base, extent), max(base, extent));
      },
    );
  }

  void hilight(Color color) {
    final (start, end) = _selection;
    if (start == end) return;

    final style = TextStyle(
        color: color.computeLuminance() > 0.25 ? Colors.black : Colors.white,
        backgroundColor: color);
    for (int i = start; i < end; i++) {
      setState(() => _style[i] = style);
    }
  }

  late final Widget highlightButtons = Padding(
    padding: const EdgeInsets.only(top: 50, bottom: 25),
    child: Row(children: [
      for (final color in [
        Colors.red,
        Colors.orange,
        Colors.amber,
        Colors.yellow,
        Colors.lime,
        Colors.green,
        Colors.cyan,
        Colors.blue,
        Colors.indigo,
        Colors.purple,
      ])
        _HighlightButton(color: color, onPressed: () => hilight(color))
    ]),
  );

  late final Widget resetButton = OutlinedButton(
    style: OutlinedButton.styleFrom(foregroundColor: Colors.grey),
    onPressed: () {
      _selection = (0, _text.length);
      hilight(const Color(0x00FFFFFF));
    },
    child: const Text('reset'),
  );

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(
        margin: EdgeInsets.symmetric(horizontal: MediaQuery.of(context).size.width / 16),
        alignment: Alignment.center,
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            highlightedText,
            highlightButtons,
            resetButton,
          ],
        ),
      ),
    );
  }
}

class _HighlightButton extends StatelessWidget {
  const _HighlightButton({required this.color, required this.onPressed});
  final Color color;
  final void Function() onPressed;

  @override
  Widget build(BuildContext context) {
    return Expanded(
      child: Padding(
        padding: const EdgeInsets.all(4),
        child: ElevatedButton(
          style: OutlinedButton.styleFrom(backgroundColor: color),
          onPressed: onPressed,
          child: const SizedBox.shrink(),
        ),
      ),
    );
  }
}