split_colored_icon.dart

import 'package:flutter/material.dart';

class SplitColorIcon extends StatelessWidget {
  final double size;
  final Color leftColor;
  final Color rightColor;
  final IconData iconData;

  const SplitColorIcon({
    Key key,
    @required this.iconData,
    this.size = 60,
    @required this.leftColor,
    @required this.rightColor,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Container(
      width: size,
      height: size,
      child: Stack(
        children: [
          Positioned(
            left: 0,
            top: 0,
            bottom: 0,
            child: ClipRect(
              child: Container(
                width: size / 2,
                child: OverflowBox(
                  maxWidth: size,
                  maxHeight: size,
                  alignment: Alignment.topLeft,
                  child: Icon(
                    iconData,
                    size: size,
                    color: leftColor,
                  ),
                ),
              ),
            ),
          ),
          Positioned(
            right: 0,
            top: 0,
            bottom: 0,
            child: ClipRect(
              child: Container(
                width: size / 2,
                child: OverflowBox(
                  alignment: Alignment.topRight,
                  maxWidth: size,
                  maxHeight: size,
                  child: Icon(
                    iconData,
                    size: size,
                    color: rightColor,
                  ),
                ),
              ),
            ),
          ),
        ],
      ),
    );
  }
}

Example: