How to set the colour axis of an overlapping contour on a contour plot?

I have two sets of data that I would like to display on the same contour plot, A as a contourf and B as a contour over the top. The problem is that A and B do not have the same range of values, A[-6 6] and B[200 300], making the contour gradient in B unreadable. Is there a way to set the caxis for for A and B separately, just to show the gradient of B over the A contourf plot?

Thank you