I have been shooting outdoors in heavy sun, people wearing red, and I am far away. I am getting so much flare on the red. I am using a lens hood. An other suggestions?
Most probably you are experiencing overexposure in red color channel. You can check this from a histogram that displays color channels separately - the red channel has a peak at the right end. Many cameras base their exposure metering on green channel, because human vision is most sensitive to green.
Unfortunately, possibility of restoring information in an overexposed color channel during post-processing is limited (if you shot RAW) or none (if you only have JPEGs).
Next time in similar situation, you could try shooting with reduced saturation setting and/or underexpose (i.e. use negative exposure compensation).