16 colour EGA palette with dithering

Help
1

Hi guys,
Looking to use Aseprite to do some background in 16 colours. I was using SciStudio’s drawing tool which uses a palette like this made up of 16 colours (MSDOS EGA) as a base then additional colours mixed with another colour:
palette

Is there a way to add to the existing CGA palette the “dithering” colours (ie one of the 16 colours mixed with another) so they appear in the palette on the top left?

Thanks,