Aysmetric Colorbar for Contourf

Hi everyone,

I have this plot, in which I used the fucntion contourf. As the Z values are not symmetric around 1, I wonder if there is a way of having Z=1 corresponding to the centre of the countour axis and have asymmetric levels for values above 1 and below 1 also in the colourbar, so that 1 is associated to the white color in this redblue colorbar. I attach the graph.

Please let me know Thanks a lot E.