Trivia: Lilac inspirations?
It's always intriguing to get inside the mind of a writer - to see what drives them, where they draw their inspiration. In the case of the Lilac card, I think I can make a good guess:
The woman in the lilac dress is very similar to Lady Roberta Meserole (or Madam, or Aunty) from Terry Pratchett's Night Watch. They both dress the same, have an unnerving ability to appear anywhere, both are clearly members of high society but mingle with anyone useful anywhere that suits them (from Mahogany Hall to Haymaker Road in Fallen London, and from The Patrician Palace to Treacle Mine Road in Night Watch), both have some connection to death (watching executions here, actively employing assassins there) and both are cryptic with the mannerism of a puppeteer.
Not to mention that the title of the card is another connection: Lilac is much more than a color in Night Watch - it's a theme that passes through the entire story. There aren't many card which name is just a color, so the card's name implies either a deeper meaning than just the color of the lady's dress, or that the dress' color has a deeper meaning.
Just visit their pages and tell me they're not the same lady!