diff --git a/source/imu.cpp b/source/imu.cpp
index 5216380..c833f0a 100644
--- a/source/imu.cpp
+++ b/source/imu.cpp
@@ -27,7 +27,7 @@ void calibrateGyroBias() {
   double sx=0, sy=0, sz=0;
   for (int i=0; i<BIAS_SAMPLES; i++) {
     sx += imu.readFloatGyroX(); sy += imu.readFloatGyroY(); sz += imu.readFloatGyroZ();
-    digitalWrite(LED_BLUE, (i%20 < 10)); delay(5);
+    digitalWrite(LED_GREEN, (i%20 < 10)); delay(5);  // green flutter during calibration
   }
   biasGX = (float)(sx/BIAS_SAMPLES);
   biasGY = (float)(sy/BIAS_SAMPLES);
@@ -41,7 +41,7 @@ void calibrateGyroBias() {
     statBiasRms = sqrtf((bxr*bxr + byr*byr + bzr*bzr) / 3.0f);
   #endif
 
-  digitalWrite(LED_BLUE, HIGH);
+  digitalWrite(LED_GREEN, HIGH);  // off after calibration
   Serial.print("[CAL] T="); Serial.print(calTempC,1);
   Serial.print("C  bias="); Serial.print(biasGX,4);
   Serial.print(","); Serial.print(biasGY,4);