Tri-Colour LED & Sonar

I am trying to create a helipad with tri-colour LED's. The idea is to have a or multiple sonar sensors connected to the LED's, and when an object is at a certain height it will change the colour. Is there a way in which to do this using an Arduino?? And if anyone has knowledge on tri-colour LED's and wether it is possible to control the colour they produce. Thanks

There are lots of examples of using sonars, and lots of examples of driving RGB LEDs, and different colour space conversions. Click on the "playground" link up there on the left.