title: change color of a circle if the user position is within its range
body: <p>I have a map on which there are some circles, each one with a certain radius, and on the page load, I get the position of the user and show it on the map. <br />
  At first all the circles are red, so I want to check if the current position of the user happens to be in any of there circles, that particular circle should get green instead of red.<br />
  what is the best way to do that?</p>