is classified as a ‘pre-noun adjectival’ in Japanese. These are a special type of word that do not conjugate, which means that they will always appear in the same form. どの
comes from the same family of words as どれ
, and is used for asking about ‘which’ thing someone will choose.
In these examples, we can see that どの
may be used to ask a question, or it may also be used in a similar way to ‘whatever’, or ‘whichever’ in English.
is only used when there are 3 or more possible choices, and どっち
） will be used when there are only 2 possible choices.
In the first example, the speaker is asking specifically about 2 options ‘red or blue’, so どっち
will be used. However, in the second example, since the answer could be any color, どの
will be used instead.