Sip (https://sipapp.io)

As a document, with the colours and gradients and other styles applied to squares. This way, I can just open the document as reference, and copy the required styles directly (sampling from the screen is a bad idea). It also means the colours can have an associated colour profile.

I definitely utilize Sip like a lot of people here. I also use Affinity Designer and Affinity Photo a lot. Both apps allow you to save + import/export color palettes. Where these applications accel is that you can create palette at a system level, application level, and document level.

For example, if I create a new project and want to reference a set of my favorite colors then I already have those available because I saved at an application level.

I also made a quick video about color management in Affinity Designer if it helps.

I use Pikka (https://redactry.com/pikkaapp)

I use the Spectrum app for Mac. It's a pretty good app, but it hasn't been updated for years.

I haven't upgraded to Sip Pro because of it, but maybe that's the better choice nowadays.

I keep a folder of offline .ASE files but I know where Illustrator keeps it's presets folder for things like Swatches and Brushes so I copy them over to there and it's like i have all my colors natively.

Yes, I keep offline ASE files

It's always part of a working document either as a symbol in Sketch or global colours in Illustrator.

Eventually it's documented either for myself or is part of more comprehensive documentation. That will be the single point of reference for future work or additions to a project.

Working in both print and digital one size doesn't fit all and a project that covers both may have a mix of cmyk, solid and rgb.

Whilst I've used CC libraries in the past, it hasn't really enhanced my work flow.

I myself use Sip, but maybe the following two links might help you:

www.coolors.co (create a profile to save your colors/palettes/schemes), there is also an iOS-app, a paid Adobe CC Add-on (for PS and AI) and a Chrome extension)

If you want to manage your colors/palettes per project in a file format, then have a look at this post: Color Creator: Photoshop, Sketch and Affinity Designer templates

Cheers mate!

CSS variables

I use sketch-palettes https://github.com/andrewfiorillo/sketch-palettes but I always have an offline version just in case.

I use Creative Cloud libraries, but that doesn't make it easy to share colours with others. Tools like Sip are interesting for local colour management and tools like lingo are interesting for collaboration, but none of the ones I tried so far are particularly great.