One of the reason the plain black and white are as popular is they are free. In general the three most popular colors for cars are black, white.and silver.
I believe the red multi-coat and Blue metallic are both striking paint colors. The white multi-coat adds real depth to the white.
I think the reason more people didn't get the red multi-coat is there was confusion with the two red colors. The red multi-coat and the signature red. The signature red is a blue red where the multi-coat is an orange red.
I am very pleased with the Titanium Metalic. I think it looks very rich and changes color based on lighting conditions. I have three Model 3 on order. Since we already have a Titabium Metalic my first choice will be red multi-coat followed by blue metallic and then white multi-coat in that order.