aller à = to suit

Question

Cecile and Chris I am more confused. Cecile seems to be saying "vous va" could be right as it can be singular but formal. Is it the "ton" which determines which "you" you use?

Accepted Answer

Hi Kay,
Just to add to Chris' answer,  I am wondering if the problem is the construction of the verb 
aller à quelqu'un = to suit someone
which is like 
plaire à quelqu'un
 https://french.kwiziq.com/revision/grammar/how-to-use-plaire-to-express-liking-something-someone
To someone, you say 'tu' to  ( friends/family) :

Cette robe te plaît ? = Do you like this dress? (Lit. Does this dress appeal to you? )
Cette robe te va bien != This dress suits you !

To someone, you say 'vous' to ( polite and respectful) 
Cette robe vous va bien != This dress suits you !
 
To a collection of people - plural  vous, assuming they are wearing the same uniform for a concert for instance :
Cet uniforme vous va bien ! = This uniform suits you!

Cet uniforme vous plaît-il? = Do you like this uniform? Does this uniform appeal to you?

Answer

Ton costume te va -- (2nd person singular, familiar form)Votre costume vous va -- (2nd person plural, or 2nd person singular, formal)
As you can see, if you start with the familiar form ton, you need to continue with the familiar form (te). If you choose the formal form votre, then you stick with that (vous). The cone bit Cécile added, which, strictly speaking, isn't part of your question, is the form to use if you were speaking of more than one costume. 
Tes costumes te vont.Vos costumes vous vont.