Gatsby's car is, "a rich cream color, bright with nickel, swollen here and there and there it's monstrous length" (Fitzgerald 64). This connects to the theme materialism because the color yellow symbolizes money and materialism.
Nick describes Gatsby's mansion as "a factual imitation of some Hotel de Ville in Normandy with a tower on one side" (Fitzgerald 5). Gatsby's mansion is symbolizing materialism because his mansion is the size of a hotel.
Nick describes Daisy's voice, “Her voice is full of money” (Fitzgerald 120). This relates to the theme materialism because her voice is her synecdoche and it symbolizes money.