Based on this hierarchical can u able to create master screen? once master screen completed in the main form can filter using domain condition.

Thanks for your answer. I don't exactly know what is a master screen. Is it easy to create that ?

I don't understand what you want: A/Select Red and have only red (without Dark red or Normal Red )\n OR B/select Red and have all subcategorizing object(RED and DARK RED and NORMAL RED)

If I select "Color" then I can see subcategories "Red" "Blue" and "Yellow". And if I select the subcategorie "Red" then I can see "Dark red" and "Normal red". Subcategories depend of Categories. And under subcategories depend of subcategories. Is it more clear now ?

I don't see any problem. Do you use parent category field of category object? On wich object do you want to use this categories?Product? In this case you have already a menu that do the job.

I don't know which code I have to use because I can't use something existant in OpenERP. For example, I have to create a new field "selection type" in "Invoice form" which one shows "Contacts" related to one partner. Another thing is to create 3 levels of categories and subcategories for articles.