I was watching a [video](https://www.youtube.com/watch?v=NPbYXYcYCuk) about various idioms that have 'machen' in them. This included the sentence 'Er macht blau', which would formally translate into English as something like 'To be absent from school/work for no good reason'.

I have two queries about this phrase:

1. I have read different resources that write the infinitive of the phrase as ['blau machen'](https://german.stackexchange.com/questions/6172/haben-blau-machen-und-blau-sein-eine-gemeinsame-etymologie "blau machen") or the separable ['blaumachen'](http://www.dict.cc/?s=blaumachen). Since this term appears to be colloquial, are both generally acceptable ways of writing the phrase, or is one more commonly used than the other?
2. The English translation above is obviously a bit verbose, but that's mainly because basically all the informal terms for absenteeism in English differ from region to region. 'To play hookie' is most used in the U.S., 'to skive' is mainly used in the U.K., and 'to chuck/pull a sickie' is an Australianism. I think 'to skip work/school' is the most widely-understood phrase for that situation, but I am not certain how commonly that is used.

At any rate, in contrast to the English phrases is 'blau machen' a widely understood, informal phrase in German-speaking countries? I bring this up because the video had translated the phrase as 'to take French leave', which is a term I had never heard of, and the equivalent for the etymologically related term 'Blauer Montag' in English is 'Saint Monday', which I don't believe is especially well-known in English either. If 'blau machen' is not widely understood, then what kinds of terms are used for being absent from work/school in an informal context?