When playing Virtual Golf you can enable a grid when around the green to learn a bit more about the slopes of the green surface. The green grid operates by means of a colour & dot system.

Essentially the dots will move in the direction in which the slope is heading and the speed of the dot will vary depending on the severity of the slope which is indicated by the colour of the green grid. The colour of the grid is a spectrum in which Blue indicates relatively flat, Yellow slight undulations & Red being significant slopes. This can be seen in an example image below.



Other factors such as elevation and green stimp are also important to consider just as when playing Golf outdoors.