java/res/color/sliding_key_input_preview_color_you.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <!-- This is necessary to add alpha to dynamic colors to a single theme -->
    <item
        android:alpha=".7"
        android:color="@color/gesture_trail_color_you" />
</selector>