Great news – glad it worked out.
Have you added the “!important” after your colour declarations? In the Codex section on child themes there’s specific mention of the Twenty Eleven dark theme .css being loaded after the child .css and so perhaps taking precedence sometimes. The advice is to use “!important” like this:
#site-title a {
color: #009900 <strong>!important</strong>;
}
The syntax matters – the !important goes before the “;”
I’d suggest ensuring you try that first. Having said that I’ve had 1 instance so far where that didn’t work for me – I’m using the dark theme in Twenty Eleven and nothing I did would take precedence over the dark.css for this partucular page element but it was quite minor so not a big problem. Very odd.
Not sure what advice you’re being given about having to purchase/upgrade (purchase or upgrade what exactly) but I’d advise caution – can’t see how purchasing or upgrading something is going to help with this query.