how do i add a choice of colours to my listings?

[digital*ghost]

I'm not 100% sure that the variation format is available in your category (not my area, sorry), but if it is, you can only create a variation listing from scratch (i.e. you can't revise a current non-variation format listing to add in colour choices).

So, if you go to create a new listing, underneath the options for category, should be an option to create variations (as long as it's available in your chosen category).

That screen shot is from the online sell your item form - if you use Turbo Lister, hopefully someone else can advise as I don't use that.... Once you click the variations option, the process is relatively intuitive, but if you get stuck on anything, someone should be able to assist. 

[kopenhagen5]

Variations - http://pages.ebay.com.au/help/sell/listing-variations.html

Turbo lister doesn't support multiple item listings so perhaps it doesn't with variations either.

[phorum_junkie*]

TL works perfectly with variations, I use it all the time. If the option isn't there then they are not available for what you are selling.