Tints apply a single color to an entire group or Symbol. Unlike fills, Tints take into account semi-filled elements with different opacities and borders. Tints are great for things like complex icons or tabs in a navigation bar — or anywhere you want to show different states through a change in color.
Applying a tint
To apply a Tint, create a group or Symbol instance then click the + in the Tint panel in the Inspector. Tints work in a similar way to fills, where you can use the Color Picker or enter a hex code and change the overall opacity. However, you can only select a solid color as a tint.
Semi-filled parts of this sample icon take on the Tint color, but with a lower opacity that reflects the original design
Using tints as overrides
To use tints as overrides with nested Symbols, you first need to apply a default tint to any Symbol instances on the Symbol Source you’re working with.
For example, in the case of a tab bar where each tab is its own nested Symbol, you’ll need to head to the tab bar Symbol Source and apply a Tint to each tab Symbol instance.
A default tint being set for nested Symbol instances
Now, when you view your tab bar Symbol instance 
, you’ll see a color icon to the right of each nested Symbol’s name in the Inspector. Clicking on the color icon will bring up the Color Picker so you can easily override the default tint for each Symbol.
How to apply a tint to a sample tab in a tab bar