Only launched in Midnight Black and Mirror Black, the OnePlus 6T flagship also received a Thunder Purple color option after a while. Sadly, it was supposed to be a China-exclusive choice, but now it seems that the US and Europe will receive it as well. The price remains the same and the sales should start on November 15, at 9 AM EST.
https://www.notebookcheck.net/Thunder-Purple-OnePlus-6T-coming-to-the-US-and-Europe.361276.0.html