lineside signals

On the BNSF line between Seattle and Tacoma which is double track, Ive knoticed that the aspects read yellow over red most of the time. Is this supposed to mean Approach-Medium. They will change to red over red when a train is in the block. But I,ve never seen green indicators so am just curious

The steady Yellow over Red is "Approach". The train must reduce speed to 30 MPH and be prepared to stop at the next signal. The next signal is most likely a "Home" signal protecting an interlocking, or junction.