Line your water line with white eyeliner or peach eyeliner, it'll instantly open up your eyes. Use a light shimmery or light metallic eyeshadow in the inner corner of your eye. This effect will not only catch the light to brighten your eyes, but really open them up! Another tip, if you want to make your blue eyes really POP, use colors such as bronzes, browns, golds, violets, and purples. Hope this was helpful!
If you want to make your eyes appear larger, you should apply white eyeliner/eyeshadow on the inner corner of your eye and white eyeliner on your waterline. The white makes them look more open (: hope this helps!