Clothing can make the shoot when getting a family portrait done. The best group portraits have eveyone wearing the same or similar colours. Solid colours are best for groups or individuals as paterns take attention away from the face(s). As for specific colours, medium toned colours in blues or greens work well. Dark colours and black are okay. White isn't bad but unless the light is soft like an overcast day, in the shade or in the studio, white can wash out in the prints. Long sleeves are better, but if you have to wear sleaveless - make sure you don't have an uneven tan on the arms such as a "farmer's tan."