Hi Malcolm,
All aircraft are required to show red, green and white lights, and there are strict limits on the viewing angles as given in the UK Air Navigation Order. The wing red and green (I always remember that the drink port is red as is the port light) must be displayed from dead ahead to 110 deg off the wing tip. The white tail light must display 70 deg either side of dead astern. The lights should also only display 90 deg in up and down in the vertical. Thus you should only ever be able to see one colour to allow you to sort out the orientation at night and give way if required by the rules of the air. Anti colls are not essential although most aircraft have them because the flashing tends to catch a pilot's eye. Hope that this helps.
Colin