UhhhG!

So I bought two gallons of Dupont Ful Thane I was able to paint everything with the first gallon(see photos below) except the bed/tailgate.

SO I cracked open the second gallon and it was not blue but Green - took it back and they mixed another - that looks about right.

Started the bed yesterday and did a test panel - seemed close but a slightly lighter blue. I painted anyway. and yes now I have two friggin colors.

Is it that hard to mix two gallons the same color?
Could the color change in the can if it sits for 2 weeks prior? (the first gallon I waited 2 weeks before paint)it is metallic (bad choice for first timer)the stuff aint cheap -

thoughts?