I disagree with blue lights on vehicles too, but I believed that it was only illegal if they flashed.

There's an old Passat that's been painted matt black with orangey-red wheels that I've seen a few times around the Lancs/Yorks border.
It has been adorned with aftermarket DRLs around its headlights.
The DRLs are RED...
The driver and passengers are of that culture that believes man-made laws don't necessarily apply.

It seems HJ is indeed wrong.

Your quote from the Government site seems clear enough, and there is also this:

www.policespecials.com/forum/index.php/topic/66035.../

Like many people, I detest the idea that cars should be some kind of "look-at-me" statement, which is what is nearly always implied by the various attention-seeking modifications, including coloured lights, under-body lighting, boom boxes and so on.

But I'm just a boring old fuddy-duddy.