Debian Emerald splash screen. Made using Debian's Emerald wallpaper by Juliette Taka (https://wiki.debian.org/DebianArt/Themes/Emerald) and modifying DebianSpace theme by Yanekyuk (https://www.pling.com/p/1222240/).
As Juliette says: "Elegantly polished and chiseled, or in their raw and natural state, gemstones can have an infinite number of shapes. With the Emerald theme, I wanted to bring light and mineral together in a clean, almost ethereal design".
Colors are turquoise, aquamarine and other mixes between green and cyan.
To install it manually, uncompress it inside ~/.local/share/plasma/look-and-feel/ (note: ~ means your home directory, such as /home/myusername)