SQL SELECT calculate probabilities

I'm trying to get some probabilities for my data
(don't try to make too much sense out of this problem as I simplified it alot, the car brand is irrevelant in my analysis)
I want to calculate probabilities of the price paid given the color of the car
So for each "color" I want to count from my database how many of each "price" was paid.

The only way I can think of doing this right now is writing a script that will call SQL function and do this for me but it looks like a lot of work.

Do you know of any sql tricks I could use to help me with this?
How would I modify my select query to do this?

----------------------

i.e. all data in data base:
red 20000
yellow 20000
red 20000
black 20000

probabilities i want to calculate and retrieve:
red (20000) = 2/4
red (30000) =  0/4
red (40000) = 0/4
black (20000) = 1/4
black (30000) = 0/4
black (40000) = 0/4
yellow (20000) = 1/4
yellow (30000) = 0/4
yellow (40000) = 0/4



mysql> SELECT cr.name, pr.name, cl.name,
    ->  FROM colour cl, priceround pr, cars cr
    ->  WHERE cl.id = cr.colour
    ->  and pr.id = cr. priceround;


+--------------------------+-----------+-----------------+
| name                     | name      | name            |
+--------------------------+-----------+-----------------+
| Honda                 | red  | 20000          |
| BMW                  | yellow | 20000          |
| Toyota               | red | 20000 |
| Ford                 | white  | 20000          |
....

priceround table
+----+-----------------+
| id | name     |
+----+-----------------+
|  0 | 20000        |
|  1 | 30000 |
|  2 | 40000 |

colour table
+----+-----------+
| id | name      |
+----+-----------+
|  1 | red |
|  2 | black |
|  3 | yellow    |