a) Masthead light means a white light placed over the fore and aft centreline of the vessel showing an unbroken light over an arc of the horizon of 225 degrees, and so fixed as to show the light from right ahead to 22.5 degrees abaft the beam on either side of the vessel
b) Sidelights - not relevant
c) Sternlight means a white light placed as nearly as practicable at the stern showing an unbroken light over an arc of the horizon of 135 degrees and so fixed as to show the light 67.5 degrees from right aft on each side of the vessel.
d) Towing lights - not relevant
e) All round light means a light showing an unbroken light over an arc of the horizon of 360 degrees.
f) Flashing Light - not relevant.
Visibility of lights:
c) In vessels of less than 12m in length:
- a masthead light, 2 miles;
- a sidelight, 1 mile;
- a sternlight, 2 miles;
- a towing light, 2 miles;
- a white, red, green or yellow all round light, 2 miles
So, in short, there is nothing in Colregs that prevents you using the light mentioned above.
However, I would worry about the effect it would have on your night vision - small 12v lights are bad enough at night! In addition, if it has a narrow focused beam, it is less visible from someone looking down at you from a height - helicopter, container ship, etc.