I've often found that colour varies dramatically between nights, hence I asked if they were on different nights
I find that different amounts of dust, haze, etc in the sky which I don't always notice visually make quite a difference to the colour of my DSLR shots (and film shots back in those days). Especially out at my country sites I get huge variations between nice rich blues/grays to very yellow dusty colours. For wiefield stuff I like that, I like keepig the uniqueness of the shots to show what it was like
Using AWB will give you unreliable variation too, best to use a fixed setting for astro stuff, I use daylight WB, but it's not the end of the world eitherway, especially if you're shooting RAW