Depends on how you are doing this. You cannot edit the default mixes for Protean. In order to change any of the styles, you will first have to create your own mix by going into Studio > Protean > Styles and click Add New Mix. You can tell it to duplicate from other style mixes. 

Once you do that, you can then edit and Save it (at the bottom). 

IF you have already done that and the changes you are making still do not apply, take a look at this post:
https://una.io/page/view-discussion?id=3256