Likely answer edit

Landsat band applications — quick lookup.

Band Spectral Applications
1 Blue Water penetration, soil–water discrimination, forest type, cultural ID
2 Green Green peak of veg. for ID + vigor, cultural ID
3 Red Chlorophyll absorption; species differentiation; cultural ID
4 NIR Veg. type, vigor, biomass; delineating water bodies; soil moisture
5 Mid-IR (1.55–1.75 µm) Veg. moisture, soil moisture, distinguishing soil from clouds
6 Thermal Veg. stress analysis, soil moisture, thermal mapping
7 Mid-IR (2.08–2.35 µm) Mineral / rock-type discrimination, veg. moisture