I was looking up a bunch of tutorials on how to use SSS skin shaders and they all said to adjust the file size of the lightmap. Mine is purple and changes back to 1026x480 whenever I try to adjust it. My renders come out looking grainy and I'm assuming this is the problem. Why is this happening?
By default tha parameter is linked by an expression to the resolution in the render globals, you need to tweak the render globals res and that will update, or you could just edit the expression and add there as much as you want, even delete the expression and type your own values.
just be careful, maybe what you need to tweak is the samples on the lightmap