Red Oscars are VERY rare. You won't be finding a 'true blood red' oscar in a pet store. Be ware of DYED fishes! They do happen with Oscars too...
In a 75G I would do an Oscar. No tank mates. If you MUST have tankmates I suggest a trio of Silver Dollars. Just a reminder tho... Anything small enough to fit into an Oscars mouth... EVentually will! So sto k tank-mates appropriately. Be sure if you DO silver dollars you get bigger ones. Oscars will outgrow them and they will possibly become lunch
LOTS of filtration is required for an Oscar tank as are frequent water changes. You cannot go bi-weekly on an oscars tank care. In my 55g I currently do 2-3 50-70% water changes a week. Nitrates climb quickly which is why I suggested an oscar only tank.