Recently I was trying to make a device that will indicate different status through different light colors.

Now after developing everything a strange thing started to happen – the RGB LED was not showing the colors properly. For example – suppose the current color is Green and then I put Red. It is not glowing pure RED, the Green pixel (the individual green pixel of the LED) is still faintly on.

After some thoughts and searches found the solution is to first turn of the LED fully

leds[0] = CRGB::Black;
FastLED.show();

and then show the new color.

Hope this helps someone.