Fix color format regexp

With old regexp for 'color' format we can pass following values:

    #casda
    #abcd
    #abcdefg    

And cannot pass:

    rgb(21,2134,213)
    rgb(21,21,213)

But now valid values may be:

    #abc
    #a3c21b   
    rgb(0,21,32)
   
And others valid HEX and RGB color values.