case (Vuforia.ImageTargetBuilder.FrameQuality.FRAME_QUALITY_NONE):

                SetMeter(Color.gray, Color.gray, Color.gray);

                break;

case (Vuforia.ImageTargetBuilder.FrameQuality.FRAME_QUALITY_LOW):

                SetMeter(Color.red, Color.gray, Color.gray);

                break;

case (Vuforia.ImageTargetBuilder.FrameQuality.FRAME_QUALITY_MEDIUM):

                SetMeter(Color.red, Color.yellow, Color.gray);

                break;

case (Vuforia.ImageTargetBuilder.FrameQuality.FRAME_QUALITY_HIGH):

                SetMeter(Color.red, Color.yellow, Color.green);

                break;

I couldn't understand the concept of coding. can you explain in more detail?