You should just use yellow color from Spanish national flag, or any other color not used for other countries.
In that case, I would have to manually add the Spanish flag's yellow color (as google doesn't offer it as one to chose from) code, which would only delay the publication of these overviews.

Anyway, I might give it a go, but problem is that that shade of yellow is similar to orange that I am using for Indian local. At least on my screen.
A long time ago, I was taught to avoid, during work presentations, more than 3 or 4 colours per graph.
You would be amazed by the number of people who have some form of colour blindness and can tell the difference between the inevitable shades of the same colour when you have more lines on the same graph.
Not saying this is the case, but actually resonates a lot.