[JSON] Fix incorrect embed color output

DiscordChatExporter.Domain/Exporting/Writers/JsonMessageWriter.cs

@@ -1,5 +1,4 @@
-using System.Drawing;
+using System.IO;
-using System.IO;
 using System.Text.Json;
 using System.Threading.Tasks;
 using DiscordChatExporter.Domain.Discord.Models;
@@ -116,7 +115,7 @@ namespace DiscordChatExporter.Domain.Exporting.Writers
             _writer.WriteString("description", FormatMarkdown(embed.Description));
 
             if (embed.Color != null)
-                _writer.WriteString("color", ColorTranslator.ToHtml(embed.Color.Value));
+                _writer.WriteString("color", embed.Color.Value.ToHex());
 
             if (embed.Author != null)
                 await WriteEmbedAuthorAsync(embed.Author);

DiscordChatExporter.Domain/Internal/Extensions/ColorExtensions.cs

@@ -9,5 +9,7 @@ namespace DiscordChatExporter.Domain.Internal.Extensions
         public static Color ResetAlpha(this Color color) => color.WithAlpha(255);
 
         public static int ToRgb(this Color color) => color.ToArgb() & 0xffffff;
+
+        public static string ToHex(this Color color) => $"#{color.R:X2}{color.G:X2}{color.B:X2}";
     }
 }