Update ReadMe.md

Author: PhasicFlow

tutorials/sphereGranFlow/RotaryAirLockValve/ReadMe.md

@@ -13,7 +13,7 @@ The problem is to simulate a Rotary Air-Lock Valve. The external diameter of rot
 <img src="https://github.com/PhasicFlow/phasicFlow/blob/media/media/rotaryAirLock.gif", width=700px>
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-	particles are colored according to their id
+	particles are colored according to time of insertion
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