Don't know exact name for design language but each company name their design system or design assets as their design language Like google name their material design as their design language. And the things about which you're asking these are illustrations.
Another method could be to use strokes with *profiles** assigned and a Blend.
Simply create a blend between a few paths with stroke profiles. You can then duplicate the blend object and move the paths around to create different variations.
I am pretty sure there are many ways one could go about this. One method is to use narrow ellipses filled with a gradient. These are all the same ellipse copied and pasted multiple times, some narrower and some wider, and some I edited by moving the red stop so it comes further up the ellipse. Everything is then cropped by using a clipping mask over a black ...
Just in case the problematic colored area is the smaller one which contains everything that a rainbow has you can try this:
Have a black background layer. Then you make the colored shape to a new layer. In Photoshop you can draw a path, convert it to selection and and fill the selection with a gradient:
(sorry for irregular looking path, you can get ...
It looks like it might just be a regular linear gradient that has been masked using a radial gradient.
You can create custom gradient using the gradient editor.
Then over a black layer, I filled a new layer with the Rainbow gradient I made. Then I used a black and white gradient to create a layer mask consisting of a radial gradient, which I ...