Is there any traditional recipe that uses béchamel (white sauce) and pomodoro (tomato sauce) mixed, making a new (orange-ish) sauce?
Is there a name for this sauce?
I often do this mixture but I've never seen it in any recipe.
Although I am uncertain about Italian cookery, this operation would seem fairly unorthodox in the French repertoire. That being said, it is customary to add cream, salt pork or bacon, and flour to sauce tomate, which essentially replicates the addition of Bechamel, although it seems Escoffier deigned not to include cream in his recipe for this mother sauce.
Perusing the section of compound white sauces in Escoffier's Guide Culinaire, there are several sauces that are at least similar to that which you described,
. Sauce Aurore - A Veloute to which tomato puree is added; for eggs, meat, and poultry
. Sauce Soubise Tomatee - A soubise is a sauce with onions that may have bechamel as a base
. Sauce Villeroy Tomatee - An Allemande to which tomato puree is added
Now I would suggest simply calling what you described "Sauce Tomate a la Creme" and not be discouraged to not find its exact replica in the canons of classical cuisine.
In Italy we usually mix béchamel and tomato sauce for "Pasta al forno" (or "pasta pasticciata") and lasagna, in order to not have a full distinction in the final dish between the two sauces and their tastes.
However this is not mandatory, but my grandma, my mum and me are used to do it (and I see some other people doing the same).
P.s. I live in Italy and I'm 100% italian :-)