(a) That's wrong. The known facts in the example do not justify drawing the conclusion that the colour of the computer was a fundamentally important term of the contract. A's main concern was to obtain a computer that would be able to run her software. It was not objectively obvious that having a red computer was so important that she would not have entered into the contract at all without that particular promise being a term of the contract.
Nor, on the given facts, was it obvious to B that the colour was so important to A. The courts often refer to the less important terms in a contract as 'warranties' to distinguish them from fundamentally important terms (conditions).
It is important to determine whether or not a term is a warranty or not because this affects the remedies available in the event of a breach of that term.