Just to illustrate, belatedly I will admit:
A broad-banded copperhead. Note the yellow tail tip. All baby copperheads have it, and it fades out when they get to about a year old.
A momma broad-banded with babies. Notice how much darker they are.
A trans-pecos, they often look much like the broad-bandeds, but the easy way to tell them apart is their amazingly patterned bellies. Which isn't so easy to get a picture of.
An osage copperhead, much lighter in color, more like hour glasses in the pattern instead of thick bands.
A northern copperhead, lighter coloring with very different saddling/banding.
Unfortunately, I haven't taken any pictures of southerns.