From Video Game Music Preservation Foundation Wiki
Gray Sky is one of the 10 different songs that are played during a regular game if using the CD audio track. It is the tenth track that is played. The tracks are played in sequence starting from Cave and ending with Gray Sky, at which point the list starts over from the beginning.
The track was composed by David Rippy using a Boss DSS-330 synthesizer and an E-mu ESI-32 sampler. Finally, the mixing and editing was done using SoundForge.
It is notable since the first 20 seconds consist of the part which later became part of Quest for Butter and Quest for Jam.
The song title has been confirmed by Stephen Rippy.