OTL, Colon discovered Indies for Castile and Leon.
Subjects of Aragon, including Catalans and Neapolitans, were aliens and as such unwelcome in Indies.
Colon had offered to serve Portugal and been turned down. Had Portugal accepted, Spain would have had no grounds to claim West Indies.
In 1492, Catholic Monarchs had been wed for over 20 years. Did Fernando participate in receiving Colon? Precisely how did Fernando and Isabel agree that Indies would be hers alone and Fernando would have no share in costs nor benefits?
Could Fernando and Isabel have agreed, before Colon set out, that Indies would be somehow shared? If yes, on what terms? What would the consequences have been?