This map seems weird, I just googled the first and biggest grey blob I knew the name of. Seems like the map is wrong.

Greenland is a danish ~~colony~~ territory and has the same holidays in the same way. The international workers' day is observed in both nations and is often a "half day off". I don't know why those two are grey.

I thought the image might be a list of countries that had a holiday on 1. may, but it doesn't seem like it. The image is form this wiki article where each country is listed. There doesn't seem to be any rhyme or reason behind the coulours. Mozabique is marked red even though it just "celebrates" the day.

It seems like this list is made by an american because it makes an effort to specify "paid public holiday" for Tunisia. Does that mean the other days aren't holidays either, except from a US perspective?

Most places public holidays are paid, that's what makes it a holiday.

Colombia is weird too because "most workers celebrate it" is enough to colour the contry red.

However, in Canada most workers also celebrate the day, but it's not red

Cuba too doesn't specify a public holiday, but is colored red.

There's more, but you get it

edit: definitely written by an amerikkkan, most other countries are 2 lines, but the US one is long as hell

For some reason we have to know about clashes with police