@Override
    public boolean equals(Object obj) {
        if (obj == null) {
            return false;
        }
        if (getClass() != obj.getClass()) {
            return false;
        }
        final Block other = (Block) obj;
        if (this._color != other._color && (this._color == null || !this._color.equals(other._color))) {
            return false;
        }
        return true;
    }