Variant alias properties cannot be converted

import QtQuick 2.0
Rectangle {
    width: 800
    height: 600
    Item {
        id: item
        property variant color: Qt.rgba(1, .5, 0, 1)
    }
    property alias colorAlias: item.color
    color: colorAlias // Doesn't work: "Unable to assign QVariant to QColor"
    //color: item.color // Works as expected
}