If I leave the language out of the code, then I can use colour just fine, like so

But if I add a language, say 'c', then it all goes pear shaped and the colour tags are no longer parsed.

That's the intended behaviour. When using language-specific tags, snippets are already color-coded. If you want to point out something specific, refer to it by line. If you absolutely have to point something out via color, use non language specific tags.

Exactly.

I thought that was blatantly obvious.

I mean if you tagged something as red with c++ code tags it would hardly stand out amongst the other mix of colours.

One possibility to consider is to allow BOLD and ITALIC using language-specific tags. Just a thought.

Bold and italic tags are already being used with the language-specific tags for specific keywords. For example, in the line the word "printf" is actually in bold in contrast to the rest of the line. However, bold font is hard to distinguish in Courier New (or any fixed width font, for that matter). In fact, when I was very anti-color, and before we had syntax-specific code tags, the reason I conceded to allowing color was because people pointed out that bold and italic tags were not doing a good enough job pointing out specific lines in code.

Wouldn't it be better if your parser at least removed the color tags from syntax-highlighted code? Some people aren't aware that color tags don't work in syntax-highlighted code tags (or they paste it from their editor, which for some reason has the code all colored), and then all we see is a bunch of BBCode crap.

Nyah. If they want to screw up their code and post without a PREVIEW, let them. We just don't have to read it since they didn't care enough to verify their post.

What if someone wants to type code that uses the [param=value] format? If someone types [x=y] in their code it should be stripped?

Well, you would only strip [color=xxx], [b], [i], etc. And considering that it would be parsed anyway if they had just used a normal [code] tag, what difference does it make?

Because this way people have a method for when they NEED to use such things in their code. If both code methods stripped them, they'd be SOL to display any code in bbcode format.