While the lawsuit won't be popular, IMO...
Slate devices started from Palm (maybe even older), but iPhone is the really popular one. Then it goes to slate touch screen phone == iPhone/Android
For Android, maybe added with the word "Droid" and that green robot for advertising material, but don't see much identity for devices in the wild.
Nokia, while still using the slate form, added bright colour. Simple and broad concept that put it in strong contrast against the sea of popular Android devices from Samsung and HTC. Yes, it's a really broad concept like used by patent trolls, but for a brand image, you can't be too detailed, it has to be easily recognized.
So if HTC is using those bright colours for their lineup because it's easily associated by consumers as a "Windows Phone", then copying or not, HTC is waving away any effort from their side to make their own branding (fighting against Nokia's already successful Lumia image) and ride on Nokia's coat tail.
Back to that again, if HTC, and the next brands, use the same bright colour for Windows Phone, then the Lumia brand Nokia has been building will be reduced into bright colour == Windows Phone. Well, if that's what happen, probably Microsoft will be as happy behind, after all they finally get someone to make strong brand image for Windows Phone that can be used by all manufacturers (something that's supposed to be Microsoft's duty).
As for the Fujitsu argument... the Japanese's local phone are behind the bamboo curtain cut off from the rest of the world. International tech news is usually focused to what happened in America (or will be affecting the consumer market in America) so those local phones won't be very interesting.
They also have many colourful phone every season in Japan, so that's not something that stands out among the market competition isn't it ?