...all of these properties of the costume have an effect on the viewer. For example, the use of colours such as red, orange and yellow (which are often associated with negativity - especially red) can make the viewer feel a sense of danger and that the costume is an indicator of what is going to happen (foreshadowing).

This also applies to the other, 'cooler' colours present in the costume. Whilst they may be used because they are complimentary to the colours already present, there are a few interesting associations to the colour purple. Whilst it positively associates with the Monarchy and being regal or rich, it is also considered as artificial and unconventional, as it's a colour least present in nature, and the first to be synthesised. This can make the character seem unreal and unnatural to the viewer. This is backed up by all of the other vibrant colours used. 

Vibrant colours also being associated with poison - hence why the viewer might feel physically unwell as a result.



This can also be a giveaway of the character. The use of unnatural colours suggests that Pennywise is a constructed persona.

Other physical attributions of the character include the bad teeth. This shows that he may have bad personal hygiene, which causes the viewer to see him as unappealing and gives them an ability to picture what his presence may be like, for example, that he would have bad breath.

There's a lot of juxtaposition going on with Pennywise's costume. For example, clowns are often seen as positive or portrayed in that way, as entertainers. However, this film plays on the fear of clowns - experienced by many people. This is probably why they made the costume so simple, rather than making it conform to horror costume conventions.

And if those subtle hints aren't enough, there's always the terrifying expression which can easily show you that he is the antagonist in the film.

Ugh, so terrifying. And definitely WAY too close.