Wanna ask a question about changing my player's material.

Here's what I wanna do, I have a char and I wanna make it half-invisible when touching sth. this char is a model I made in Max, and have imported, all my mats are in the SkinnedMeshRenderer Component. I know I can change material by coding "gameObject.renderer.material.color" if my material is directly patched on a GameObject. But I totally have no idea how to change material in a SkinnedMeshRenderer... I have searched some way on the web, yet they are all referring to Shader, I totally have no idea on Shader... so still I wanna find a ordinary coding way to make it...

Thanks for help!