Milton Waddams wrote:
Is it ok to use the masthead tricolor light while under sail and then
simply add a white all around light above it when under power?What is
the minimum separation of vertical lights for a 22 foot sailboat?

No. When you turn on the engine you become a power boat. The
masthead light, sometimes called the "steaming light," must be higher
than the sidelights. I don't think it would be easily possible to
satisfy the requirements in the ColRegs with the tricolor. Also,
while the tricolor might make sense offshore, I think its wise to have
deck height lights for inland work.

From Annex I of the ColRegs:
(d) A power-driven vessel of less than 12 meters in length may carry
the uppermost light at a height of less than 2.5 meters above the gun-
wale. When, however, a masthead light is carried in addition to side-
lights and a sternlight or the all-round light prescribed in rule 23(c)(i)
is carried in addition to sidelights, then such masthead light or all-
round light shall be carried at least 1 meter higher than the sidelights.
(g) The sidelights of a power-driven vessel shall be placed at a
height above the hull not greater than three quarters of that of the
forward masthead light. They shall not be so low as to be interfered
with by deck lights.
(h) The sidelights, if in a combined lantern and carried on a power-
driven vessel of less than 20 meters in length, shall be placed not
less than 1 meter below the masthead light.

And from the Inland version:
(d) The masthead light, or the all-round light described in Rule
23(c), of a power-driven vessel of less than 12 meters in length shall
be carried at least one meter higher than the sidelights.