My Will Goodwin that I planted this year bloomed a few times but was never blue ?? Why? Its ALWAYS a pale purple.
The flowers are described by most sources as a lavender blue.....it's not what I'd describe as a true blue :-) If you do a Google image search, you will see that coloring is somewhat variable. I find this to be true with many clematis cultivars - light exposure, soil conditions and even the age of the flower will have a lot of influence on specific flower color.
True GG, not to mention that pictures can also be affected by the type of camera that you take pictures with so if you are comparing the clematis in your garden to pictures posted on the web, that can also lead to confusion.
IMHO no Clematis is true blue such as you find in 'Heavenly Blue' morning glories or 'Nikko Blue' hydrangeas. They are all tinted by purple. Not a problem for me, I love purple. Some are certainly bluer than others though.
My Will Goodwin was close to a pale true blue last year. This year's bloom was more pale blue lavender.
My HF Young was really blue. At least I think that is the name of it...sorry if I got it wrong. It had some lavender in it but lots of blue tones.