Here's my solution:
toolbar.navigationIcon?.mutate()?.let {
it.setTint(theColor)
toolbar.navigationIcon = it
}
Or, if you want to use a nice function for it:
fun Toolbar.setNavigationIconColor(@ColorInt color: Int) = navigationIcon?.mutate()?.let {
it.setTint(color)
this.navigationIcon = it
}
Usage:
toolbar.setNavitationIconColor(someColor)