My eyes change their color?? help plz!?

hello. got bright brown eyes (maybe hazel??) the thing is dat when i go to the countryside (i got a house there) they get more beautiful and bright.. WHY and how can i make them be like dat always!!!?? also, some say that some people change the colour of their eyes with age. My bro had brown eyes and now are very hazel. Will that happen to me?