Answer:
testing vision is called visual acuity & it is done through Landolt's chart (contains symbols of different sizes & u tell the opening while u sit on a chair 6 metres away), better now by computer; may also b done through neutralizing the red reflex by lenses of different powers till u get the result.
colour vision is tested by Ishihara test; which is a card containing coloured circles; if u colour blind u will mis-read the number formed by combination of circles through contrast colour background
Vision is tested subjectively by using charts having letters or signs of different sizes . Objectively vision is tested by refraction using plane or concave mirror, more acurately with a computer assuming accommodation of lens is taken into cosideration.
Color vision is tested by 1)Homegren`s wools 2) Ishihara`s pseudo iso chromatic charts 3)Edridge Green`s color perception lantern and 4) Nagl`s Enameloscope.