Use material colors instead those from w3schools

[mueller-ma]

Since it's material design icons, we should go for material colors: https://material.io/guidelines/style/color.html

[metbril]

I like this suggestion. Have you already made a mapping of the used set in the README to those colors?

[mueller-ma]

Not already. I would suggest having the mapping in mdi.py and the names in yaml files.