left join and where

hello,
I'm a beginner and I have a trouble with SQL and Access 97
I try to explain the problem:

I have a table colori:

ID colore
1 red
2 blu
3 green

and a table Vendite

ID colore anno quantita
1 red 1 10
2 blu 1 20
3 green 2 30

I want a query that return all "quantita" but only for a year (for example
if year =1, I don't extarct green)
The result must be:

colore anno quantita
red 1 10
blu 1 20
green
------------------------------------

I use this SQL code

SELECT colori.colore, vendite.anno, sum(vendite.quantita)
FROM colori
LEFT JOIN vendite ON colori.colore=vendite.colore
WHERE vendite.anno=1 OR vendite.anno Is Null
GROUP BY colori.colore, vendite.anno

But the result is

colore anno quantita
red 1 10
blu 1 20

How can I get the correct result

Thank's for the help

Andrea