Silk Naturals

I was wondering if there was a chart that matches up the cream foundations to Mac foundation colors?

I am trying to order a SPF50 foundation for when I am outside all day, they align their colors to Mac foundation color charts.

I wear an N30 in the cream foundation.

If it helps any, I wear N30 (N40 if I'm more tanned), and got matched to MAC NW18. NW18 is more neutral and less cool than the other NW shades.