And easy = quicker & cheaper, the deer color vision study can be done with some simple medical observations over a short period of time in one location by one or two people
Fawn death/ coyote studies take hundreds of people in multiple states years to make any kind of meaningful correlation between the numbers. And those results might take a decade or more to process and factor out the data that was tainted by other factors.
That being said there are plenty of studies that have been done but the factors are too complex to simply nail down to X coyotes = y dead fawns.
https://www.themeateater.com/wired-to-hunt/whitetail-management/what-is-killing-americas-fawns
Our staff attended the annual Southeast Deer Study Group meeting back in February 2012 and the theme revolved around how predators are changing the way deer populations are managed in some areas across the Southeast. We are still learning about the behavior and general ecology of coyotes and...
westerveltwildlife.com
In my case I am, here in PA the majority of the deer where I hunt are extremely skittish around people as they spend several months of the year being hunted. Additionally in many cases the terrain does not allow for them to be seen prior to being well within their ability to see you.
I have several places I hunt where 60 yards is the farthest that I can see and you definitely have to time your movements or they will bust you. In my experience camo seems to give you a bit more leeway in your movements compared to solid colors if your timing is less than perfect.