diff --git a/app/operations/layer-modes-legacy/gimpcolor-legacy.c b/app/operations/layer-modes-legacy/gimpcolor-legacy.c
new file mode 100644
index 0000000000..1fff7e5442
--- /dev/null
+++ b/app/operations/layer-modes-legacy/gimpcolor-legacy.c
@@ -0,0 +1,255 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpcolor-legacy.c
+ * Copyright (C) 2024
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include "../operations-types.h"
+
+#include "gimpcolor-legacy.h"
+
+
+#define GIMP_HSL_UNDEFINED -1.0
+
+
+void
+gimp_rgb_to_hsv_legacy (gdouble *rgb,
+                        gdouble *hsv)
+{
+  gdouble max, min, delta;
+
+  g_return_if_fail (rgb != NULL);
+  g_return_if_fail (hsv != NULL);
+
+  max = MAX (rgb[0], MAX (rgb[1], rgb[2]));
+  min = MIN (rgb[0], MIN (rgb[1], rgb[2]));
+
+  hsv[2] = max;
+  delta = max - min;
+
+  if (delta > 0.0001)
+    {
+      hsv[1] = delta / max;
+
+      if (rgb[0] == max)
+        {
+          hsv[0] = (rgb[1] - rgb[2]) / delta;
+          if (hsv[0] < 0.0)
+            hsv[0] += 6.0;
+        }
+      else if (rgb[1] == max)
+        {
+          hsv[0] = 2.0 + (rgb[2] - rgb[0]) / delta;
+        }
+      else
+        {
+          hsv[0] = 4.0 + (rgb[0] - rgb[1]) / delta;
+        }
+
+      hsv[0] /= 6.0;
+    }
+  else
+    {
+      hsv[1] = 0.0;
+      hsv[0] = 0.0;
+    }
+
+  hsv[3] = rgb[3];
+}
+
+void
+gimp_hsv_to_rgb_legacy (gdouble *hsv,
+                        gdouble *rgb)
+{
+  gint    i;
+  gdouble f, w, q, t;
+
+  gdouble hue;
+
+  g_return_if_fail (rgb != NULL);
+  g_return_if_fail (hsv != NULL);
+
+  if (hsv[1] == 0.0)
+    {
+      rgb[0] = hsv[2];
+      rgb[1] = hsv[2];
+      rgb[2] = hsv[2];
+    }
+  else
+    {
+      hue = hsv[0];
+
+      if (hue == 1.0)
+        hue = 0.0;
+
+      hue *= 6.0;
+
+      i = (gint) hue;
+      f = hue - i;
+      w = hsv[2] * (1.0 - hsv[1]);
+      q = hsv[2] * (1.0 - (hsv[1] * f));
+      t = hsv[2] * (1.0 - (hsv[1] * (1.0 - f)));
+
+      switch (i)
+        {
+        case 0:
+          rgb[0] = hsv[2];
+          rgb[1] = t;
+          rgb[2] = w;
+          break;
+        case 1:
+          rgb[0] = q;
+          rgb[1] = hsv[2];
+          rgb[2] = w;
+          break;
+        case 2:
+          rgb[0] = w;
+          rgb[1] = hsv[2];
+          rgb[2] = t;
+          break;
+        case 3:
+          rgb[0] = w;
+          rgb[1] = q;
+          rgb[2] = hsv[2];
+          break;
+        case 4:
+          rgb[0] = t;
+          rgb[1] = w;
+          rgb[2] = hsv[2];
+          break;
+        case 5:
+          rgb[0] = hsv[2];
+          rgb[1] = w;
+          rgb[2] = q;
+          break;
+        }
+    }
+
+  rgb[3] = hsv[3];
+}
+
+static inline gdouble
+gimp_hsl_value (gdouble n1,
+                gdouble n2,
+                gdouble hue)
+{
+  gdouble val;
+
+  if (hue > 6.0)
+    hue -= 6.0;
+  else if (hue < 0.0)
+    hue += 6.0;
+
+  if (hue < 1.0)
+    val = n1 + (n2 - n1) * hue;
+  else if (hue < 3.0)
+    val = n2;
+  else if (hue < 4.0)
+    val = n1 + (n2 - n1) * (4.0 - hue);
+  else
+    val = n1;
+
+  return val;
+}
+
+void
+gimp_rgb_to_hsl_legacy (gdouble *rgb,
+                        gdouble *hsl)
+{
+  gdouble max, min, delta;
+
+  g_return_if_fail (rgb != NULL);
+  g_return_if_fail (hsl != NULL);
+
+  max = MAX (rgb[0], MAX (rgb[1], rgb[2]));
+  min = MIN (rgb[0], MIN (rgb[1], rgb[2]));
+
+  hsl[2] = (max + min) / 2.0;
+
+  if (max == min)
+    {
+      hsl[1] = 0.0;
+      hsl[0] = GIMP_HSL_UNDEFINED;
+    }
+  else
+    {
+      if (hsl[2] <= 0.5)
+        hsl[1] = (max - min) / (max + min);
+      else
+        hsl[1] = (max - min) / (2.0 - max - min);
+
+      delta = max - min;
+
+      if (delta == 0.0)
+        delta = 1.0;
+
+      if (rgb[0] == max)
+        {
+          hsl[0] = (rgb[1] - rgb[2]) / delta;
+        }
+      else if (rgb[1] == max)
+        {
+          hsl[0] = 2.0 + (rgb[2] - rgb[0]) / delta;
+        }
+      else
+        {
+          hsl[0] = 4.0 + (rgb[0] - rgb[1]) / delta;
+        }
+
+      hsl[0] /= 6.0;
+
+      if (hsl[0] < 0.0)
+        hsl[0] += 1.0;
+    }
+
+  hsl[3] = rgb[3];
+}
+
+void
+gimp_hsl_to_rgb_legacy (gdouble *hsl,
+                        gdouble *rgb)
+{
+  g_return_if_fail (hsl != NULL);
+  g_return_if_fail (rgb != NULL);
+
+  if (hsl[1] == 0)
+    {
+      /*  achromatic case  */
+      rgb[0] = hsl[2];
+      rgb[1] = hsl[2];
+      rgb[2] = hsl[2];
+    }
+  else
+    {
+      gdouble m1, m2;
+
+      if (hsl[2] <= 0.5)
+        m2 = hsl[2] * (1.0 + hsl[1]);
+      else
+        m2 = hsl[2] + hsl[1] - hsl[2] * hsl[1];
+
+      m1 = 2.0 * hsl[2] - m2;
+
+      rgb[0] = gimp_hsl_value (m1, m2, hsl[0] * 6.0 + 2.0);
+      rgb[1] = gimp_hsl_value (m1, m2, hsl[0] * 6.0);
+      rgb[2] = gimp_hsl_value (m1, m2, hsl[0] * 6.0 - 2.0);
+    }
+
+  rgb[3] = hsl[3];
+}
diff --git a/app/operations/layer-modes-legacy/gimpcolor-legacy.h b/app/operations/layer-modes-legacy/gimpcolor-legacy.h
new file mode 100644
index 0000000000..64f15cddae
--- /dev/null
+++ b/app/operations/layer-modes-legacy/gimpcolor-legacy.h
@@ -0,0 +1,36 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpcolor-legacy.h
+ * Copyright (C) 2024
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef __GIMP_COLOR_LEGACY_H__
+#define __GIMP_COLOR_LEGACY_H__
+
+
+void   gimp_rgb_to_hsv_legacy   (gdouble *rgb,
+                                 gdouble *hsv);
+void   gimp_hsv_to_rgb_legacy   (gdouble *hsv,
+                                 gdouble *rgb);
+
+void   gimp_rgb_to_hsl_legacy   (gdouble *rgb,
+                                 gdouble *hsl);
+void   gimp_hsl_to_rgb_legacy   (gdouble *hsl,
+                                 gdouble *rgb);
+
+
+#endif /* __GIMP_COLOR_LEGACY_H__ */
diff --git a/app/operations/layer-modes-legacy/meson.build b/app/operations/layer-modes-legacy/meson.build
index 7fa8409fbc..58a0dd3bb6 100644
--- a/app/operations/layer-modes-legacy/meson.build
+++ b/app/operations/layer-modes-legacy/meson.build
@@ -1,4 +1,5 @@
 libapplayermodeslegacy_sources = [
+  'gimpcolor-legacy.c',
   'gimpoperationadditionlegacy.c',
   'gimpoperationburnlegacy.c',
   'gimpoperationdarkenonlylegacy.c',