From 7e5aac2e2b50cd5015c140928f20b3c7aac937d8 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Fri, 27 Mar 2026 20:50:28 +0530
Subject: [PATCH] Allow setting color table value to none via OSC 21

---
 kitty/colors.c        |  5 +++++
 kitty/window.py       | 11 ++++++++---
 kitty_tests/screen.py |  3 +++
 3 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/kitty/colors.c b/kitty/colors.c
index c0e0ac6f1..a901bed34 100644
--- a/kitty/colors.c
+++ b/kitty/colors.c
@@ -586,6 +586,11 @@ set_color(ColorProfile *self, PyObject *args) {
     if (!PyArg_ParseTuple(args, "Bk", &i, &val)) return NULL;
     self->color_table[i] = val;
     self->dirty = true;
+    if (val == NULL_COLOR_VALUE) {
+        bool semantic, dynamic = palette_generation_is_dynamic(global_state.options_object, &semantic);
+        if (dynamic) generate_256_palette(self, self->color_table, semantic);
+        else self->color_table[i] = FG_BG_256[i];
+    }
     Py_RETURN_NONE;
 }
 
diff --git a/kitty/window.py b/kitty/window.py
index 4ff0ac395..7b6b7156c 100644
--- a/kitty/window.py
+++ b/kitty/window.py
@@ -49,6 +49,7 @@ from .fast_data_types import (
     GLFW_RELEASE,
     GLFW_REPEAT,
     NO_CURSOR_SHAPE,
+    NULL_COLOR_VALUE,
     SCROLL_FULL,
     SCROLL_LINE,
     SCROLL_PAGE,
@@ -577,9 +578,13 @@ def color_control(cp: ColorProfile, code: int, value: str | bytes | memoryview =
                 else:
                     if 0 <= colnum <= 255:
                         val = val.partition('@')[0]
-                        col = to_color(val)
-                        if col is not None:
-                            cp.set_color(colnum, color_as_int(col))
+                        if val:
+                            if (col := to_color(val)) is not None:
+                                cp.set_color(colnum, color_as_int(col))
+                        elif colnum > 15:
+                            cp.set_color(colnum, NULL_COLOR_VALUE)
+                        else:
+                            cp.set_color(colnum, get_options().color_table[colnum])
         else:
             if attr:
                 delattr(cp, attr)
diff --git a/kitty_tests/screen.py b/kitty_tests/screen.py
index 4fec4185b..06bbb82e7 100644
--- a/kitty_tests/screen.py
+++ b/kitty_tests/screen.py
@@ -1616,6 +1616,9 @@ class TestScreen(BaseTest):
         q({'selection_background': ''})
         self.assertIsNone(s.color_profile.highlight_bg)
         q({'selection_background': '?'}, {'selection_background': ''})
+        opts = self.set_options({'palette_generate': 'semantic'})
+        q({'213': ''})
+        q({'213': '?'}, {'213': Color(216, 125, 215)})
         s.color_profile.reload_from_opts(opts)
         q({'transparent_background_color9': '?'}, {'transparent_background_color9': '?'})
         q({'transparent_background_color2': '?'}, {'transparent_background_color2': ''})