Shader Mixer - how to make a User Parameter use the linear color picker?

agent unawares

This is probably a dumb question, but how in Shader Mixer do you get a user parameter that uses the linear color picker like the Iray Uber shader? All the ones I make come up with the RGB picker.

agent unawares

Got it, you have to drag to auto add from a brick that has that parameter. What on Earth.