The plastic they're using (hard-coated polycarbonate) is, I believe, the same plastic used on many of the Nokia Lumia phones which a lot of people say feel much higher quality than other, regular plastic phones. That said, the 5C is the cheaper option and it isn't going to feel as good as the aluminium of the 5S. I don't however think it will be anywhere near as cheap-feeling as other phones (e.g. the Samsung Galaxy S4 which has been described as feeling "greasy").
Those are all just staged for ads (unless you think you can't listen to the Beatles Red Album on a blue nano and vice versa) except for the latest one, which came out after the Nokia devices.
I'm sure someone did it before (I seem to recall IE5 letting you change the interface to match the early iMac colours) but your comment (and a quick glance at the linked image) is misleading as it stands.
The Nokia is staged for ads too. You can change the highlight color to be whatever you want. Additionally, many WP apps have a solid colored tile that doesn't respect the user's color choice.
Not sure I agree with Nokia's formulation of the saying. I prefer "Imitation is the sincerest form of flattery", which makes a lot more sense. Imitation isn't the best form of flattery - it's actually quite an irritating form of it - but it is the sincerest form (since, unlike verbal flattery, it's rarely feigned: you imitate because a thing is worth imitating, not to flatter the imitatee).
