Finally I painted strawberries with my students too.
Not an easy task when you have to study and understand their shape, with the tiny effects of light and shadows, for the best result. The color matters a lot too. Many reds turn out dull when dry and if the strawberry is completely red it's also a disadvantage. Choose those that have variety in color, light and dark... or invent some lighter zones.
Ad some Indian yellow to your red or use a Vermillon as you brightest red, for cast shadows any blue (light or dark) or grey mixed with a little of the strawberry's colors here and there will do.
The lighter the berries are the more luminous they will seem.