Answer:
In case of sunstroke the body is unable to sweat because the body is dehydrated.
The temperature of the body won't increase further because there can be no more evaporation in body as it cannot sweat more from the skin surface.
The skin dissipates the heat and cools the body preventing the overheating of the body.
The skin appears to be red in color because the blood is dilated and dissipiated into the whole body for cooling.