Eyes are naturally blue if there is no color pigment inside them, because the molecules inside the eye scatter blue light in much the same way that the sky is blue because the molecules in the atmosphere scatter blue light
Mammals have 2 different pigments that give their skin, hair and eyes color. They are eumelanin (dark brown to black) and phaeomelanin (yellow to red). Most people around the world have brown eyes because eumelanin is present. People with dark skin have eumelanin in their skin cells, and people with black hair also have eumelainin on their hair shafts. Yellow hair is the result of no eumelanin on the hair but a small amount of phaeomelanin. Red hair is the result of no eumelanin and a high concentration of phaeomelanin. Similarly, white skin is the result of a lack of eumelanin, and only small amounts of phaeomelanin that give skin a slight pinkish color.
If there is no eumelanin or phaeomelanin in the eye, then the eyes are blue colored, because of scattering of blue light. If there is no eumelanin and a small amount of phaeomelain, then the result is green eyes, because yellow mixed with blue give a green color. People with hazel eyes have lots of phaeomelanin but no eumelanin. The lack of eumelanin is a recessive trait. That means both your parents must have passed along copies of genes that fail to manufacture eumelanin to you.
Because people with green or blue eyes have no pigment or very small amounts of light absorbing pigments in their eyes, they are more susceptible to eye cancer, because harmful UV light can damage cells inside the eye. People with brown or black eyes have pigments that can protect their eyes by absorbing the UV light. One way to protect the eyes is to wear glass lenses sunglasses, because glass blocks UV light from entering the eyes. Wearing plastic lens sunglasses do not protect the eyes, and actually make things worse because plastic does not absorb UV light and the dark lens makes the iris open wider to let more light in. Therefore wearing plastic sunglasses actually allow more UV light to enter the eye to do more damage than if no sunglasses are worn.
Both your parents may only have a single copy of the recessive blue-eye gene. If so, then you have a 25% chance of being blue eyed or green eyed.