Glympse changes the color of the arrow or dot on the map according to whether the user you are watching is actively sharing or expired. The colors in Glympse for iPhone are slightly different from the colors used in Glympse for Android. Below is a key to what each color indicates.
Arrow = the person is actively moving
Dot = the person is standing still
Android
Grey = expired
Blue = you
Green = someone else's active glympse you are watching
iPhone
Grey = expired
Orange = you
Blue = someone else's active glympse you are watching