Boot sizing.

[Dekadenz]

Before you jump to any conclusions, yes I already attempted to research this topic inside and outside of this website.
I am buying a pair of rocky s2v boots to ruck/run with before I leave with my 18xray in February. I live in the middle of no where and the closest retailer with them is over 2 1/2 hours away, I have no transportation capable of making the journey. Now my question, would the boot size for all rocky boots be universal? Could I go to my local hunting store fit a pair of rocky hunting/work boots and use that size when I order a pair of duty boots off the internet? Also since they should be broken in by the time I leave I hope to take them to selection as my (dry) second pair of well worn in boots. I assume I should get them in desert tan for this reason?
Thank you, any help is greatly appreciated.