Paper/paper-server/nms-patches/net/minecraft/server/gui/ServerGUI.patch

--- a/net/minecraft/server/gui/ServerGUI.java
+++ b/net/minecraft/server/gui/ServerGUI.java
@@ -160,6 +160,7 @@
         this.e.forEach(Runnable::run);
     }
 
+    private static final java.util.regex.Pattern ANSI = java.util.regex.Pattern.compile("\\x1B\\[([0-9]{1,2}(;[0-9]{1,2})*)?[m|K]"); // CraftBukkit
     public void a(JTextArea jtextarea, JScrollPane jscrollpane, String s) {
         if (!SwingUtilities.isEventDispatchThread()) {
             SwingUtilities.invokeLater(() -> {
@@ -175,7 +176,7 @@
             }
 
             try {
-                document.insertString(document.getLength(), s, (AttributeSet) null);
+                document.insertString(document.getLength(), ANSI.matcher(s).replaceAll(""), (AttributeSet) null); // CraftBukkit
             } catch (BadLocationException badlocationexception) {
                 ;
             }