Shifting through the seasons

If the descent of colors is purposeful:

just weeks ago we felt yellow
jackets menace the thin skin

The muscadine falls blue to the trail
and sets off the hickory yellow,

What keeps the gray squirrel bounding
tree to tree and the chipmunk on edge

when the blackened moon moves

You mentioned yellow after saying "blue", which reverses the effect and didn't give it a direct transition. And then here:

the sun dip, and your hand fall

Descent of yellow...but we've already moved past that?

If that wasn't purposeful...it should've been.

What keeps the gray squirrel bounding
tree to tree and [what keeps] the chipmunk on edge

I liked the ending. Just a fall poem.

The days have now shortened when
just a week ago we felt yellow
jackets menace the thin skin
at our wrists.

Tight decscription I really like, but you might have forgotten an "a" here

The muscadine falls blue to the trail
and sets off the hickory yellow,
the reds of the dogwood and sumac.
I look for the mirrored moon tracks
that mark the passage of deer,
the rare buckeye slipping from its case.

Again a very tight description, and a very well use of color what sort of bothers is the repeating of "yellow" which you've allready used above. As for me I think "hickory yellow" should stay like that and it is rather the jackets which you can give another colour

What keeps the gray squirrel bounding
tree to tree and the chipmunk on the edge
in the shattered shale,
what stills our mouths
and sets our wandering minds to winter?

I believe here that there are 2 questions being asked, the first one you leave open, no question mark and the second you do add a question mark to. I could understand why you'd want the first one to be left open but it kind of blurs the whole image - a very nice one by the way - so maybe a comma could make things clearer

I've felt the warmth give way --
the sun dip, and your hand falling
from mine like a leaf that burns bright
just so it could let go -- and the trail blazes disappear
with the dusk. We trust our feet to take us home
and our mouths to find the winding way
back to words.

Here I pointed out falling, as I'm not sure about what you meant here, is it "the hands fall" or a "falling hand" both seem to fit the situation quite proper but on my opinion a "falling hand" is little more suitable.
The second thing I pointed at "We trust our feet....." Well this is breathtaking well well done Brad, fascinating indeed

In shallow sleep
when the blackened moon moves
over February's bare and brittle
branches, you'll feel the keen bite
of autumn chill and seek
my hand when I am gone.

I like the ending as in apart from what you've written above, I just have the feeling it all doesn't suite so well But this is your poem and you closed the way you wanted to, since we all differ in thoughts, to my concern you might have just deleted this last stanza. Your last stanza's ending was great But this stanza is also very well descripted

Overall I liked your once in a while use of colour I believe you chose them very well

Well done Brad

~Cheerios, Chandni