ExifTool
参考:
Just Color Picker
参考:
Just Color Picker – best free colour tool for Windows and macOS
画面上の色取得ならカラーピッカー Just Color Picker がお勧め | Beginner’s Design Note (reikawatanabe.com)
Paint.NET
参考:
Paint.NET – Free Software for Digital Photo Editing [Official]
paint.net | Microsoft Store [公式]