color is irrelevant - it's chemistry that matters.  there are a number
of high quality non-silicate anti-freezes on the market, no two with the
same color afaict.  if you /knew/ what was in there, maybe you could
stop worrying.

there's two drain plugs - bottom right of the rad [left if you're facing
the engine] and the drain plug on the engine block.  if it's a d-series,
it's a largish hex plug lower left as you face the motor.  you'll need a
new gasket when replacing.  and you'll need to repeat this process at
least twice - the coolant in the climate control system never drains.

one last thing - don't use tap water when refilling, use distilled.

Is the existing coolant dull, dark green or a luminous bright green?

Dull, dark green is older Honda OEM. Luminous bright green is evil
aftermarket.

The best way to "flush"is simply to drain it all -- including pulling the
block drain. Then stick a garden hose in the rad filler neck, and spray
water in until all orifices run clear. Let it all drain, plug up the
openings, then refill with genuine Honda Type-2 premix.