How to change Tab Stacking color scheme?

• The tab stack color is selected randomly from the following 16 colors.

• The color format is: <color> [ <percentage> | <length> ] [, <color> [ <percentage> | <length> ]]*

• See https://developer.mozilla.org/en/CSS/-moz-linear-gradient

If a top line is desired, set a color like: red 2px, -moz-dialog 1px

pref("extensions.tabutils.colorStack.0", "#50C2F8 20%");
pref("extensions.tabutils.colorStack.1", "#60FDC8 20%");
pref("extensions.tabutils.colorStack.2", "#67FF91 20%");
pref("extensions.tabutils.colorStack.3", "#81C3F8 20%");
pref("extensions.tabutils.colorStack.4", "#94B1FB 20%");
pref("extensions.tabutils.colorStack.5", "#ADEBE5 20%");
pref("extensions.tabutils.colorStack.6", "#AF9FF5 20%");
pref("extensions.tabutils.colorStack.7", "#BACEF8 20%");
pref("extensions.tabutils.colorStack.8", "#C9FF6F 20%");
pref("extensions.tabutils.colorStack.9", "#EAAEE6 20%");
pref("extensions.tabutils.colorStack.a", "#EACFA7 20%");
pref("extensions.tabutils.colorStack.b", "#F7A6B9 20%");
pref("extensions.tabutils.colorStack.c", "#F88371 20%");
pref("extensions.tabutils.colorStack.d", "#F8B7B3 20%");
pref("extensions.tabutils.colorStack.e", "#F8D7DA 20%");
pref("extensions.tabutils.colorStack.f", "#FFCF6E 20%");