If one of those headless machines is running Linux, this script [1] says it will control Hue using Redshift [2].
[1] https://github.com/jonls/redshift/issues/189 (the Gist in the comment)
[2] http://jonls.dk/redshift/
Edit:
There's also this, which is a bit more polished: https://github.com/deuxpi/redshift-hue
And this, which even has a GUI! https://github.com/poinck/lampe