In the Dutch political context, the word 'purple' refers to the coalition of social democrats and liberals. In theory, it is a coalition that puts an end to the classic political divide between left and right. As a result, the Parliament does not hold debates. Rather, it deliberates. Dutch politics is an oasis of calm, as it has to be.
Conflict is counter-productive.
No single party has ever had anything approaching an overall majority in parliament, so coalition government is inevitable. For decades, the Christian democrats played a pivotal role in the struggle for power. Sometimes they formed coalitions with the social democrats, sometimes with the liberals. The Christian democrats called the shots, the rest followed at a polite distance. The result was predictably consistent government policy.