To get Imagemagick running on OS X (if you don’t have Brew installed, go here first):
brew install imagemagick
You’ll then have the utility installed with alias ‘convert’ …
To tint an image with a specific HEX color this works:
convert input.jpg -colorspace gray -fill '#EB1423' -tint 100 tinted.jpg
This one is what I prefer instead:
convert input.jpg \( -clone 0 -fill '#EB1423' -colorize 80% \) -compose multiply -composite tinted.jpg
And for posterity’s sake, my favorite utility macros are here. They use OS X’s Automator.