[From Clematis For Everyone, pp. 10-11:] Purple, blue and mauve are the predominant colours, although regrettably the blue is not a clear blue as with a delphinium [another member] of the Ranunculaceae family... The reds also are not a pure colour since the nearest true red contains shades of blue or purple... The pinks are of various pastel shades, frequently having two tones, giving a bar or star like appearance... Even the deepest shades of pink fade gently in bright sunlight... A large-flowered, deep buttercup yellow clematis is yet to be produced... the yellows are represented by the deep yellow, nodding flowers of C. tangutica var. tangutica... white-flowered clematis are very elegant... when plants are late in producing their flowers due to bad weather conditions, some clematis flowers often open green, the correct colour appearing later as the flowers age and the tepals are subjected to the sun's rays... [often] the flowers do not completely attain the true colour... [occurs most often] with white, or very pale pink or pale blue cultivars...