This is quite an easy mod - really a collection of a couple of mods already known. Bear in mind that certain colors (and flashing lights of the front) may well be illegal for on-road use in your jurisdiction!
I bought one of those "Knight Rider" LED strips, although this one actually has multiple colors and lighting configurations. I fitted it in front of the rubber seal that sits under the hood when it's closed. I popped the plastic clips off, then attached the strip using 3M tape, then replaced the rubber seal. This ensured that it was held firmly in place and wasn't pushing anything out of alignment.
It comes with a small black radio receiver that I mounted under the left side of the fender, also with 3M tape.
Drilled a hole through into the engine bay (I have a CVT so used the hole where the clutch stuff would go). Then threaded a wire through, spliced it to the positive of the receiver. The negative wire was grounded.
Screw in place where hole was drilled:
Screw seen from other side:
In the cabin, the wire was connected to a toggle switch I installed into the unused plastic cover next to the driver, that in Europe has a couple of switches on it. It was a tight squeeze but the switch fit - you could use smaller buttons if you want.
The other end then went to a fuse extender connected to fuse number 4 - for me this is always on.
Put everything back in place - it looks nice and tidy. Viola