Where to get Gnome Night Light source code?

I had thought of asking this question on Stackoverflow but there all the "Night Light" references are for Windows 10 Night Light. Too bad Microsoft and Gnome Developers didn't draw straws for who would call their application "Blueshift" or whatever.

Preamble aside... How do I get source code for Night Light (Gnome version)? Would source code for Mutter and dconf / gsettings also be needed?

I understand there are different versions 3.34.1, 3.35.1 and 3.36 beta:

• GNOME's Mutter 3.35.1 Fixes The Night Light Mode On Wayland

Since the other answer just provided the source code for the UI which is not very helpful, here is the actual logic if someone else is searching for this:

https://gitlab.gnome.org/GNOME/gnome-settings-daemon/-/tree/master/plugins/color

I found it by searching for relevant commits on the GNOME Gitlab.

considering Ubuntu 18.04

I think its here for Ubuntu 18.04 http://in.archive.ubuntu.com/ubuntu/pool/main/g/gnome-control-center/

some of the content of apt show gnome-control-center

APT-Sources: http://in.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
Description: utilities to configure the GNOME desktop
 This package contains configuration applets for the GNOME desktop,
 allowing to set accessibility configuration, desktop fonts, keyboard
 and mouse properties, sound setup, desktop theme and background, user
 interface properties, screen resolution, and other GNOME parameters.

http://in.archive.ubuntu.com/ubuntu/pool/main/g/gnome-control-center/

you can check your gnome-shell version and then download that version number from above link.. for example if you want for 3.34 download that version number.