FaLLeN I don't use mods to highlight bosses, i have mods for all models (special, player, weapons) but they don't "glow" just changes the skins. I just use sound to shoot where i hear it coming from. If you played fps like counter-strike for more than 15 years like me you would know this. Time is experience.
The only one that become more visible is the hunter because of the yellow stripes which can be seen from certain distance.
The boomer also has blue clothes but is not very visible in the dark like in the second image with a boomer behind the tree.