I am currently making a curriculum for the basics of HTML and CSS.
Revisiting CSS Levels, I have written in the past about it:
The important thing to remember is to pattern it after the Levels of HTML wherein we must begin with Accessibility and Usability in mind.
And from there on, we build towards Visual Design.
Using this as basis, one could argue that Colors and Typography are “nice-to-haves”.
Can your design stand in black and white?
Can your design stand in a serif font?
Yes, it should.