Is it legal to have led lights mounted inside fairing and under tank? If it is, are some colours banned? I was thinking about green or multi coloured, but wired so they work with brake light
                                                                                                                                                                             

Its a bit tricky, it is not illegal to have lights under your tank or in the fairing, however they must not be blue, though a lot of people do use blue on their cars, however as ancillary lighting they should be on a separate switch, so they can be switched off without affecting the other lights, this comes under construction and use for road vehicles.
From an MOT point of view, you cannot have them wired to your brake lights, as the mot rule is a red light showing to the rear, but as you won't need an mot for 3 years you may well be alright.
It may also cause a bit of a distraction to whoever is behind you if you brake and your bike suddenly lights up like a christmas tree.

Whassup, Naomi....pimping the new ride? :)

The kind of lighting you seem to be asking about comes under the term 'additional non-standard lighting'.

Tezza covered it nicely, but felt the need to clarify a few bits:-

* cannot have any lights pointing forward other than white - (until you pass halfway)

* cannot have any light pointing back other than red (until you pass halfway)

* cannot have any lights blinking other than orange turning indicators

* on the side lights are fine as long as they:

* are not red, or blue or green - but this is open to individual cases and interpretation in a court. Best keep it simple.

* are not blinking

* the source of the light is not visible, just the glow

The last point is relevant to neons and LEDs.

And then, there's the final part that says 'they must not be a distraction to other road users'.

So...give some thought to how bright / discrete the lighting is compared to your main obligatory lighting.

I think your K would look pretty cool with accent lighting.
I also agrees with Tezza:-
Fit them to a switch and avoid attaching them to any moving parts.
Wheels, handlebars and wipers on cars are examples.

Don't connect them to the legal fixed lights - including brakes.

If you get pulled over, be your usual polite and unassuming self. It might be to just say how cool your bike looks :)

For the beagles, link to the UK regs below.

http://www.legislation.gov.uk/uksi/1989/1796/contents/made#(Tii)iicolourlightshownlampreflector