diff --git a/src/xrt/include/xrt/xrt_defines.h b/src/xrt/include/xrt/xrt_defines.h
index ef1231296..763ce91b6 100644
--- a/src/xrt/include/xrt/xrt_defines.h
+++ b/src/xrt/include/xrt/xrt_defines.h
@@ -133,6 +133,56 @@ struct xrt_vec3
 	float z;
 };
 
+/*!
+ * A 3 element colour with 8 bits per channel.
+ *
+ * @ingroup xrt_iface math
+ */
+struct xrt_colour_rgb_u8
+{
+	uint8_t r;
+	uint8_t g;
+	uint8_t b;
+};
+
+/*!
+ * A 4 element colour with 8 bits per channel.
+ *
+ * @ingroup xrt_iface math
+ */
+struct xrt_colour_rgba_u8
+{
+	uint8_t r;
+	uint8_t g;
+	uint8_t b;
+	uint8_t a;
+};
+
+/*!
+ * A 3 element colour with floating point channels.
+ *
+ * @ingroup xrt_iface math
+ */
+struct xrt_colour_rgb_f32
+{
+	float r;
+	float g;
+	float b;
+};
+
+/*!
+ * A 4 element colour with floating point channels.
+ *
+ * @ingroup xrt_iface math
+ */
+struct xrt_colour_rgba_f32
+{
+	float r;
+	float g;
+	float b;
+	float a;
+};
+
 /*!
  * A pose composed of a position and orientation.
  *