No. If you have a "X is Y" sentence, the construction with "to" needs Nominative, the construction with a form of "być" needs Instrumental.
But "Jabłko jest czerwonym" would be wrong anyway, because Y goes into Instrumental only when it is a noun phrase: Jabłko jest czerwonym owocem (An apple is a red fruit). If Y is just an adjective, it stays Nominative.
But could we even have a "noun TO adjective" construction?
Eg. Ryba to czerwona
Or would that need to have 'jest' in there as the object has no actual noun, only an adjective.
(I know that the longer construction... Ryba to czerwona zwierzę would be ok)
2... Oh wait, incidentally....
Ryba to czerwona zwierzę OR ryba to czerwone zwierzę
Ie... Does the declension of RED have to match the feminine gender of rybA or the neuter gender of animal?
And whatever your response, is that then the rule only for 'x to adjective y' or for the 'x jest adjective y' version too.
Sorry for the layered questioning
"Ryba to czerwona" is just wrong. You can only use the 'to' construction if you have nouns (noun phrases) on both sides. It has to be "Ryba jest czerwona".
It has to be "czerwone zwierzę" because 'red' describes 'animal', not the fish. "Ryba to czerwone zwierzę" or "Ryba jest czerwonym zwierzęciem" (no matter the construction, 'red' still describes the animal).
Perhaps this could make some things clearer: https://forum.duolingo.com/comment/16373167