If the word has the gender ”en”, then it’s ”vit”, if it’s neuter (ett) then you add a -t to the adjective, making it ”vitt”.
- Hunden är normal. (The dog is normal)
- Barnet är normalt. (The child is normal)
- En ful stol. (An ugly chair)
- Ett fult bord. (An ugly table.)
I've also picked up in later lessons that plural nouns take -a. Is that correct?
Indeed. The adjective has to agree with the noun in gender and number. That is, it has to follow those properties of the noun if that makes sense.
I am learning a great deal with my Swedish lessons at Duo Lingo.
The Color section is the first section I had have problems with. The Discussions with other learners help with my problems, but they are not a good substitute for having a Tips and Notes section when introducing a new topic as all of the other sections do. Specifically, there should be notes for the endings taken by adjectives---colors in this case---and there should also be an explanation for the use of the word "de" because this word is used in a way that is completely new for me.
Again, I appreciate the efforts of everyone here who is helping. My comment is made in the spirit of pointing out places where a complete beginner may stumble seriously.
Well, it is similar to the possessive adjectives which we previously learned. Scroll down at this page with a browser for those tips and notes. https://www.duolingo.com/skill/sv/Possessives
Here is a list of colors: https://www.duolingo.com/comment/6072830 and the adjective tips and notes come later.
Can we say : Vit är X or should it be Vitt
or depending on X if definite/indefinite or singular/plural?
That word order is not used normally, only in some poetry or similar. If used, the form of vit depends on gender etc, just like with "X är vit" (which is described above). Unless you mean X as in e.g. "Vitt är min favoritfärg" (white is my favourite color), where vitt is the subject. There you use the neuter form of the color.