Twenty Ten change footer seperator colour

Its coming from your style.css line 1237
and its the border-top you see in the style below.

#colophon {
    border-top: 4px solid #000000;
    margin-top: -4px;
    overflow: hidden;
    padding: 18px 0;
}

If you wish to change it or edit it, simply change the border-top attributes. Like 4px to 1px or #000000 to something like #333333 will give you grey.
To be sure that you keep the theme ready for future updates though, it is recommended that you make a simple child theme and simply make the change in there, if you are unfamiliar with making a child theme, we can help you with that.

I have checked that loads, and there were no values. Turns out I needed to check all of the colophon tags! There are about 4… changed it now, thank you so much.

Quite okay creating a child theme, been using one for over a year now ??

Thanks again for your help!
Christopher