The middle stripe of a flag
Around 2010, Wikipedia's lavender article showed #734F96 as dark lavender. It said the color stood for the middle band of the bisexual pride flag, Pantone 258. The activist Michael Page designed that flag. It was first shown on December 5, 1998, at the first birthday party of BiCafe. The flag has a pink band on top, a blue band at the bottom and a purple band in the middle fifth.
Not quite the flag color
Today the bisexual pride flag article gives Pantone 258 as #9B4F96. The blue and green values match #734F96, but the red value is 155 instead of 115. So the flag's purple is brighter and pinker than dark lavender.
Dark lavender is much deeper than floral lavender, the color of the flower. It is close to royal purple. White text on it reaches a contrast ratio of 6.39 to 1.

