You can do something like this:
Mouse mymouse;
Camera mycam;
Pick mypick;
Entity myent;
mycam.Create();
if(mymouse.IsDown())
{
if(mycam.GetPick(mypick,Vec3(mymouse.GetX(),mymouse.GetY(),1000)))
{
//Do something when the mesh GetPicked
myent = mypick.entity;
myent.SetColor(Vec4(1,0,0,0));
}
}