"rgb(194,67,202). "
I have checked pigment values on several pictures and agree that when blue exceeds red, the flower is usually very lavender and may have some "blue' tendencies. One picture I found on the internet had very high saturation for both red and blue (like 230) and was very deep lavender. Problem is that it was not a picture that I took and who knows how much it was altered in a photo editing program. People say that there are not blue dahlias but many of the deep lavender flowers have lots of blue RGB numbers. If the blue number exceeds the red number, you really see some blue. 
I found this color on a portion of a dahlia floret. Red119, Blue 198.
