Some input on dying and creating a custom color (sorry, this is gonna be long!):
https://www.ritdye.com/color-formulas/
RIT does color charts that show the combinations of their basic dye colors, and proportions that you need, to achieve more custom shades. I mean, obviously, you're not going to use RIT dye on suede boots (!) BUT, dying a ratty old tee you were going to toss or donate, could be a very useful way to experiment with color and figure out what shade of green you really want, and how to get to that color, if you're starting with a boot color that isn't already on its way to the color you're after.
Let me give you an example: I once bought a light grey - almost silver - J Crew cotton pencil skirt at Goodwill. Beautiful, but not my color. I thought how much I really wanted a true violet-blue shade, but I didn't know how that dye would interact with the silvery color that was already there. So I found a raggedy old tee that was a similar grey to the skirt, cut it into pieces, and worked with RIT dye in shades of blue and purple, until I got the color that I wanted. Then I dyed the actual skirt, and the color was gorgeous. (and then I sold it on eBay because, as it turns out, I loved the color .... but not against my pasty white legs).
I have a pair of greenish/khaki nubuck bootie-pumps.... ("shooties"? I get lost in the lingo)... that I've been thinking about dying navy blue, but they have a fabric sock component that is also khaki. If I eventually try this, my plan is to thrift a garment in a similar shade, work out the RIT dye proportions to get to the navy I want, and then try to similarly mix leather dye for the shoes.
However... I agree that OTK boots are a big project to take on! I would search for a highly-reviewed cobbler in your area, and take dyed color samples of fabric you've worked on, so they can really see what it is you want.
Also, I think green is really only Christmas-sy if you're wearing red with it, or white faux fur, or both.