I found something similar in SO: android-tv Changing text color and font of browse fragment rows header
Following topic answer I came up with this:
<style name="CustomRowHeaderStyle" parent="Widget.Leanback.Row.Header">
<item name="android:textColor">@color/red</item>
</style>
But this changes not only text that appears above the rows, but also navigation drawer text. I would love to get answer for the first one (having different color for navigation drawer item headers).