Gray, black, and white likely symbolize different stances or conditions. For example, ‘Blessed are those who wash their robes’ (Revelation 22:14) suggests white represents purity and righteousness.
A possible interpretation is that gray emerges from the interplay of white and black.
If we assume:
White symbolizes the correct stance (righteousness, truth),
Black symbolizes the wrong stance (sin, error),
Gray represents indecision or wavering faith,
then the combination of these conditions—especially the prevalence of gray and black—corrupts God’s land.