A generation mix is the most compact statement of a country's energy politics available. It shows what has to be imported, what is exposed to fuel prices, what is exposed to weather, and how quickly any of it is changing.
The fuels are stacked in a fixed order so the same fuel keeps the same colour on every country page — colour follows the fuel, never its rank in that particular country. Only the mutually exclusive fuel categories are plotted: Ember also publishes roll-ups like "Fossil" and "Renewables", and stacking those alongside their components would double-count.
Seasonal shape is real and large. Compare a month with the same month a year earlier, not with last month.