Remember, a linking verb <span>is a </span>verb which<span> connects a subject to its predicate without expressing an action.
"Was" is the linking verb.
</span>
<span>It expressed a feelings of cheery and bright, but at other times it was dark and shadowed by evil.</span>
The narrator in Frankenstein is Victor Frankenstein. As this paragraph is taken out of context one can only assume that he is the one talking (as the narrator). First person- Person speaking Second person- Person being spoken to Third person- Being spoken about
So looking at this text we can conclude that it a someone speaking so that gives us first person.
Therefore that would make this first person (victor).
Hope I helped! Let me know if you need more help or would like further explanation! :)