How to make chroma and Luminance gradient for ue4 triangle?

Greetings!
There are enough tutorials on how to make a triangle in the ue4 material editor.
But nothing similar about how to paint over this triangle with a gradient similar to chroma-luminance!
At the same time having the ability to change the hue of chroma.
Any ideas how to achieve this?

TriangleChromaPH