@NonNull
        public Builder setNavigationBarColor(@ColorInt int color) {
            mDefaultColorSchemeBuilder.setNavigationBarColor(color);
            return this;
        }
Sets the navigation bar color. Has no effect on API versions below L.

To ensure good contrast between navigation bar icons and the background, Custom Tab
implementations may use {@link View#SYSTEM_UI_FLAG_LIGHT_NAVIGATION_BAR} on Android O and
above, and darken the provided color on Android L-N.

Can be overridden for particular color schemes, see {@link #setColorSchemeParams}.

@param color The color for navigation bar.
customtabs/src/android/support/customtabs/CustomTabsIntent.java