You dont need to create extra theme settings for a custom color as it will cause you a headache later if you needed to reinstall the theme
You can simply add another line of code in custom.css to setup the default color with targeting body tag except color schemes classes
body:not(.taP_colorScheme1):not(.taP_colorScheme2):not(.taP_colorScheme3):not(.taP_colorScheme4):not(.taP_colorScheme5)
.grpAdmin {
--theme-grpAdmin: 0, 0, 255; /*<--- This is the default color in raw rgb*/;
color: rgb(var(--theme-grpAdmin));
}
basically, this will change the .grpAdmin color value but only if body tag has no classes like (taP_colorScheme1, taP_colorScheme2...)
In your case you also do not need to use raw rgb color values in palette theme setting as its complicated to customize the colors. (Im only using raw rgb values in palette because ips uses almost all kinds of color with rgb)
you can simply use HEX values in palette like --theme-grpAdmin: #fff; you will also need to remove the rgb tag in the color property color: var(--theme-grpAdmin);