If I was to have multiple pages which were similar how would I rank?
For example, if I decided to feature separate pages for Black, Blue, White and Red BMW cars how would I rank for the search term “BWM car”?
Does google choose to rank all 4 similar pages or would it only pick 1. Or would Google Panda kick in and decide not to show any due to low-quality pages?
Generally with duplicate content, the one it perceives as the original will rank best.
In that example I would not consider different colours to be a big enough difference to warrant separate pages.
With cars I would page by model (and maybe variants of) and mention on one page which colours it is available in.
I have pointed you in the past to Google videos explaining how search works. Please watch them again, as you still seem to be confused.
Unless Google sees your entire site as untrustworthy - in which case it will probably remove it from the index altogether - the content of one page will not affect the ranking of another. If your Mercedes page is deemed the best fit for a search query, it will be returmed high up in the search results, whether your BMW pages, Audi pages, Ford Anglia pages or whatever rank highly for their respective keywords or not.