Ideally, the palettes provided by your theme should provide for a pleasant, harmonious color scheme and there would be no need for color hex codes. Of course, many of us cannot leave well enough alone and will want to alter the provided palette. Hex codes are a great way to copy a color from elsewhere, but they’re not very intuitive for coming up with one’s own unique color. HSV and similar slider interfaces are more intuitive for that.
Each one of us will have our own preferences, so each color selection method should be available to us.
Thanks for your clarification
You mentioned HSV as a slider, I searched HSV and HSV slider in Plugins and did not find it, where can I find it and see how it relates to colors
Thanks for your help
Sorry for any confusion I may have caused. I’m not sure there’s a specific HSV color picker plugin for WP. I was thinking in broader terms, such as the color pickers in graphics software such as GIMP or PhotoShop.

This is what I generally use when picking my own custom colors. You can choose colors in any manner that suits you best. There are similar tools online, but with these you end up copy/pasting hex codes into your own app or CSS anyway.
There are generic color picker code libraries available so you can integrate similar color pickers into your own project. They are not WP specific, so you’d need to have some coding expertise in order to integrate them into WP. For example, I found this after a brief search. The 4 slider example is HSV plus a transparency slider. It ought not to take much more coding effort to include a sample box showing the currently selected color and hex code.