Shaders are like resource packs, each one has it's own visual affects and you probably just aren't using the same shaders I am. I personally use RudoPlays' Shader. http://rudoplays.com/shaders/
Not sure if this works for Mac, but it worked for me on PC and I don't see why Mac would work differently.
I just got a computer that is powerful enough to use shaders and let me say shaders makes everything sexier
