It was Doppler that told us the change of frequency of sound let you
know if the object was coming towards you or away. Now we think of
Hubble next using red,and blue to show if an object is coming at us or
away. This is not true it was to guys named Huggins,and Fizeau. In 1869
Huggins figured out that Sirius was moving away from Earth at 20 miles a
second. Hubble came into the picture when he picked up on this and
applied it to galaxies,and he told us galaxies got redder,and redder
they increased their speed away from us with distance. In other words,
the universe was expanding. Hubble got a Nobel Bert