Those variables have been renamed in the most recent releases.
For a searchable list of all Sass variables, check the documentation here:
And for the Sass variables related to a component (with descriptions), check the component’s API page:
Some of the components do not have the Sass variables documented yet, see this issue for more info: https://github.com/driftyco/ionic/issues/8785
Make sure you are settings the variables prior to the import for the ionic theme here:
@import "ionic.theme.default";
Take a look at the conference app for some examples of overriding Tab’s Sass variables:
Please keep in mind this will override the default tab colors, but if you add a color attribute to the tabs component that will take precedence. 