I love these letters because of how light and cheerful they are to look at. The thin and thick lines add a sense of stability with room for play and goofiness without being over the top. It is the perfect amount of seriousness and playfulness.
This is a typography style inspired by Piet Mondrian's famous works. It is very interesting because it not only uses the colours in an appropriate style in reference to Mondrian, there is also a three dimensionality aspect added in. This allows for the typography to go even further than it's inspiration.