So how tho decide wich jersey to wear in a football match? What Serie A and UEFA rules say

In recent weeks there have been some quite embarrassing cases of jersey selection. Starting with Sivasspor-Basaksehir, with locals playing in the snow in a white suit, confusing themselves with the whitewashed field. Or, even more resounding - given the presence of the public at the stadium - the AC Milan-Inter Milan derby of 2016, in which the teams had both played with the first jerseys, in that season both with a lot of black, and neither from the stands nor on tv could you distinguish well who the Rossoneri were and who the Nerazzurri were. On his return, after twenty years, AC Milan returned to play a derby with the white shirt. But to decide which jersey to play with there is a clear procedure. 

There is one for each championship, and it's not just about mating to do during races. In fact, there are also rules for undercuts, for the use of shorts and socks, for the presence of which (and how many) sponsors can go. Every year, this vedemecum of the aesthetics of the championship is updated according to the news accumulated over the years or, if any, due to accidents in previous seasons.

In addition, UEFA prohibits the display of sponsors of companies that produce super alcohol or tobacco. In practice, there are no problems for beer - Heineken is the main partner of the Champions League -, while for any brands of liquor or wine there are restrictions. No problem for betting sites. In any case, each team qualified for a European competition must comply with the rules on sponsors of the host team federation, and therefore, comply with that rule. At example, in Serie A teams cannot play using betting sponsor, and last year, in Champions League tie Atalanta-Valencia, Spanish side used a jersey with no sponsor - beacause they had Bwin.