diff --git a/protobuf_definitions/message_formats.proto b/protobuf_definitions/message_formats.proto
index c7f1924b..3d1883b8 100644
--- a/protobuf_definitions/message_formats.proto
+++ b/protobuf_definitions/message_formats.proto
@@ -1553,6 +1553,15 @@ message MultibeamDiscovery {
   MultibeamErrorFlags error_flags = 8; // Error flags specific for the connected multibeam device.
 }
 
+// Color filter used to render the multibeam sonar fan.
+//
+// The fan renderer maps each echo intensity (0..255) to a color through this
+// lookup table. The drone keeps the last filter received in memory and applies
+// it to the sonar RTSP stream; grayscale is used until one is set.
+message MultibeamColorFilter {
+  bytes rgb = 1; // 768 bytes: 256 consecutive R,G,B triplets, indexed by echo intensity.
+}
+
 // Error flags for multibeam sonar devices.
 message MultibeamErrorFlags {
   /*
diff --git a/protobuf_definitions/req_rep.proto b/protobuf_definitions/req_rep.proto
index d167c2dd..796735eb 100644
--- a/protobuf_definitions/req_rep.proto
+++ b/protobuf_definitions/req_rep.proto
@@ -275,3 +275,21 @@ message GetCvModelsReq {
 message GetCvModelsRep {
   repeated CvModelInfo cv_models = 1; // All installed models, including models that are not running.
 }
+
+// Request to set the color filter used to render the multibeam sonar fan.
+message SetMultibeamColorFilterReq {
+  MultibeamColorFilter color_filter = 1; // The color filter to apply.
+}
+
+// Response after setting the multibeam color filter.
+message SetMultibeamColorFilterRep {
+}
+
+// Request to get the color filter currently used to render the multibeam sonar fan.
+message GetMultibeamColorFilterReq {
+}
+
+// Response with the current multibeam color filter.
+message GetMultibeamColorFilterRep {
+  MultibeamColorFilter color_filter = 1; // The current color filter. Empty rgb means none is set (grayscale).
+}