Joeys costume is very much down to your personal preference Harvey.
There are lots of options ( and as always you can spend some time looking through the many pics of different Joeys on this Board as inspiration )
But colour-wise ...he is usually determined by the rest of your set, as it is nice to have him in a contrasting colour to anyone else ..which gives the audience as many different colours to look at as possible character by character.
This rings the changes through a show
For example ..you seldom (if ever ?) see a Joey dressed in the same sort of Red as Punch ...they are onstage together so much , it would be odd if they were both in red.
Unless you are one of the rare folk who have a Punch that has a lot of green on the red costume..or a Punch that is dressed in blue ( and there are one or two folk whos puppets are like that ...Tony James for example has a blue Punch ) ...then we can safely say your Punch will mainly be Red .
Policeman in Dark Blue . Croc Green etc ...Is the Judy in your new wooden set in a dress that is green ? ...or Blue ? or some other colour? ( often a spotted or flowery or Gingham fabric ...but it will still come down to being one 'over-all' strong colour )
Pick something for Joey that sets him apart from these other main characters.
Perhaps this is a reason there are quite a few "white' Joeys around ...this is also because of the famous illustration of Josef Grimaldi and his white clown outfit .

CvdC made a whole range of Joeys a few years back using this Grimaldi pic as the concept ...and very fine they look too.



And here is a splendid Geoff Felix version:

Rod Burnets Clown uses a printed fabric with pink sweets ( licorice allsorts ?) all over .
Quite a few favour crazy prints or Diamond patterns .
You really are spoiled for choice .
And Joey is the one puppet in any set that you can really personalise to be your own trademark look.
So you are quite right to give him plenty of consideration before you start to build and costume him.
Good Luck with it all
Richard