When I used Optifine I could enter the settings/options for the shaders in the video menu.
Like changing color of the light and water. Disable the waving effects on leaves and such.
I can't do that with the Iris Shaders.

It would be nice to have a settings feature for the shaders because I find the orange color of the light at night and when you are in caves are a bit annoying.

This is already being tracked in #663.