What is the most common way to say that 'something is red' (or any other colour)?
I ask this because grammar books (for example, Yip Po-ching and Don Rimmington's Chinese: A Comprehensive Grammar) usually make a distinction between 'gradable' and 'non-gradable' adjectives, as in 他很高 'he is tall' v. 這是假的 'this is false'. But colour adjectives seem to be a bit of a grey area and I'm not sure if using 很 or 是...的 is more appropriate (and when 色 sè can or should be added to the plain colour adjective).
So, if I want to say 'this car is red', which of the following options is better? Are they all valid?
1. 這輛汽車很紅。 2. 這輛汽車很紅色。 3. 這輛汽車是紅的。 4. 這輛汽車是紅色的。