True Colors is a novella in Thea Harrison's Elder Races series. It's free right now at Kindle and Kobo US and Kindle UK. And probably at Kobo UK, but I don't check there...
Kindle US:
https://www.amazon.com/dp/B0738PH85C
Kobo US:
https://www.kobo.com/us/en/ebook/true-colors-28
Kindle UK:
https://www.amazon.co.uk/dp/B0738PH85C