Taxonomy page by views with two arguments?
Based upon my read of your question there may be several things to address here.


View is not overriding your URL.  The address you have in the URL should be unique and intended to call the view just as if it is any other piece of content.  Do not have more than one piece of content with the same address, can only confuse things. Ignoring aliases for a moment, that means you cannot create a view with the path of taxonomy/term/tid, but you can create one called taxonomy/term/tid/facts. adding the fourth level of the URL makes it a unique address.
You are not defining a taxonomy page with terms from two vocabularies. To provide the content you desire you should create a view with the desired URL name. 
A taxonomy page has a URL of taxonomy/term/tid. You can provide it with an alias, but that can confuse your thinking.  The first thing Drupal always does with an alias is convert it back to the original path.  So anything that uses the URL, such as Views will not see the alias, it only sees the original path. That means that that if the paths you desire, such as red/gm are aliases, they will not be seen by the view.
A view can have multiple paths using the % wildcard.  If you created a view with a path of /cars/%/brand Then your view will be called by Drupal for any value placed in the % location of the path.
A view path should always have a static name for the first and last positions of the path.  In your examples above for red/GM you basically have an URL of %/%which would be assigned to just about everything.


To create your desired View content you may want to try the following:


Define two vocabularies for brand and color, and/or anything else you want in the categorization.
Create a content type that includes fields for these two vocabularies and give the content URLS following the formula similar to  `cars/%(color)/%(brand)/ 
Create a view with a path something like cars/%/%/view The word 'view, in the path can be anything you desire.
Define the view to display whatever content you want.
Create two contextual filters, the first defined to read a term from the color taxonomy and the second to read the brand.  Views will use the value of the first % for the first contextual filter and the second % for the second filter.


That should get you started, although I suspect you will have at least one more round of questions before it works for you (It always does.)  There are a lot of previous questions on this site whose answers will help solve the details for you.  There is also an excellent video series 'Taming the Beast' that can show you everything you need to know about views.