When chicken is done cooking and ready to eat the juices of the chicken will run clear and there will be no more pink color to the chicken or any blood in the chicken.
If the juices are not clear and there is still pink color or blood to the chicken then it needs to cook a bit longer until the pink color is gone, the blood is gone and the juices run clear.
A good way to tell whether or not the chicken is done is to use a meat thermometer and when the internal temperature of the chicken reaches at least 160 F the chicken is done.
Put the meat thermometer into the chicken meat near the inner thigh (between the leg and the breast, but make sure you're not hitting bone).
Once the temperature reads at least 160 F then it's done.