I'm not overly familar with the Sony Vaio range, though to me it looks like the only difference in names based on color is the trailing letter (eg P11Z/W is white, P11Z/R is red). As to Dell, I don't think you can level that complaint at them at all, their
product range is very well segregated and I've certainly never seen differently named models varying only by colour.
Apple's laptop range is only easier to understand because they basically have 2 models: "Cheap, small, underpowered" and "Large, overly powerful and very expensive". Unless you count the Air, but you'd have to be crazy drunk to buy one of those things.