Of all the characters I drew with chalk at the GalaCon I must admit Starlight Glimmer was the most challenging for me.
The reason is that her mane and tail both consist mostly of shades of purple (with the exception of the light aquamarine stripe) and her torso too is of a light purpleish color. In addition to that much of her mane and tail are darker than I could get the chalk unless I use a lot of coal along with it.
I have not so far found a proper black chalk and with coal as black it is a bit of a "love/hate thing" for me. On the one hand coal really does darken the chalk and if used in combination with chalk, the chalk "binds" the coal so it won't dust all over the place. This works really well to provide shading. On the other hand the use of pure coal (mostly for the black in the eyes) can become a messy business which is why the black in the eyes is something I usually do last when creating chalk drawings. Combined with chalk the coal not just darkens but also kind of desaturates the chalk color which is why I wanted to go without it in the mane and tail of Starlight Glimmer.
Here is one alternative version of the photo in which I used a color enhancing filter (which I think makes her look too intensively purple though).
Several other artists, most notably Easterforest92 and a brony from Asia whose name I sadly don't know (he had drawn her on Friday already so she had sadly been washed away by Saturday's rainfall) had drawn Starlight too, but I think I was the only one who drew her with her post reformation hairstyle and actual cutie mark instead of the = sign ;)
Helzg helped to fill in Starlight's fur within the outlines and I was very gratefull for the assistance because literal Starlight was on it's way when near sundown chalk Starlight Glimmer was finished and there was one more character to draw who had to be done under rather challanging (lack of) light conditions.
I'm not sure if Kelly Sheridan, who voices Starlight, ever got to see all the Starlights in front of the forum, but maybe she ends up seeing some of them online.