THE LILAC ZONE
Not only is the color unusual, but this cultivar has the propensity to occasionally generate mutations in the form of bicolor panicles, panicles composed of both white and purple florets! Based on my own personal observations, I can attest that this is true, as I have observed and photographed said mutations in this cultivar in two separate collections!
Note the picotee effect in the florets upon close observation
'Comtesse Horace de Choiseul' mutation at Highland Park
In the lilac world, one of the most curious cultivars is 'Comtesse Horace de Choiseul'. This cultivar is technically defined as being double-flowered and white. In the past, it has been called "the grey lilac", which I can certainly understand why when viewing it from a distance. I believe that this lilac tends to have an overall greyish hue due to the fact that each floret actually has a faint picotee effect. The casual observer may not notice it from afar, but if you look at the florets closely, it is clearly there. The combination of the faint purple with the white seen in all of the florets combined creates the appearance of the lilac looking slightly grey.
'Comtesse Horace de Choiseul' mutation at the Arnold Arboretum