diff --git a/homeassistant/components/smarttub/light.py b/homeassistant/components/smarttub/light.py
index 8c6010568e2..2cdcefb372b 100644
--- a/homeassistant/components/smarttub/light.py
+++ b/homeassistant/components/smarttub/light.py
@@ -4,8 +4,8 @@ from smarttub import SpaLight
 from homeassistant.components.light import (
     ATTR_BRIGHTNESS,
     ATTR_EFFECT,
+    COLOR_MODE_BRIGHTNESS,
     EFFECT_COLORLOOP,
-    SUPPORT_BRIGHTNESS,
     SUPPORT_EFFECT,
     LightEntity,
 )
@@ -43,6 +43,9 @@ async def async_setup_entry(
 class SmartTubLight(SmartTubEntity, LightEntity):
     """A light on a spa."""
 
+    _attr_color_mode = COLOR_MODE_BRIGHTNESS
+    _attr_supported_color_modes = {COLOR_MODE_BRIGHTNESS}
+
     def __init__(self, coordinator, light):
         """Initialize the entity."""
         super().__init__(coordinator, light.spa, "light")
@@ -89,7 +92,7 @@ class SmartTubLight(SmartTubEntity, LightEntity):
     @property
     def supported_features(self):
         """Flag supported features."""
-        return SUPPORT_BRIGHTNESS | SUPPORT_EFFECT
+        return SUPPORT_EFFECT
 
     @property
     def effect(self):