Add the ability to delete colors

[Verity-Freedom]

I want to delete new colors that I added for more precise work with extension.

They're still deleted but only if you added a new color, so it's not really urgently, it just would be more convenient.

[zero-top]

This component directly uses https://github.com/bgrins/spectrum, which has not been updated for a long time. If there is no major problem here, no modification will be made, but PR is also welcome.