Hey, are demon eye lights like the ones seen in the image below legal? 

Is it mainly illegal if the coloured light hits the road? 

Blue light showing is a no no. Could be seen as impersonating plod.

Its a technicality but a plod who hasn't got laid in a while would jump on it. Then you would be refitting the std lights and getting a re mot as well as any other penalties they can find, small number plate? noisy pipe?

Read this, specifically concerning blue lights but also summarises vehicle light rules in general: http://www.ukemergency.co.uk/blue-light-use/

Damn, so I literally can't legally have any colour light emitting from my bike...? What would class are the interior on a bike? haha 

You can as far as I know use coloured lights that "reflect" from below your vehicle, as long as they are not visible from the side ie tucked up inside the frame or faring.