For flowers without any hair covering the colour of the perianth is usually unambiguous, even if the flower starts off green or whitish and then gradually assumes its pink or red colouration, as in for example, H. verrucosa.

Other flowers which have a dense ferruginous indumentum on the outside of the perianth, as in for example H. vittata, may also appear reddish and have been scored as such here. They will also have been scored for their internal colour, usually white or yellowish, where this is known.