st difficulty is here to know of what Order the Colour of any
Body is. And for this end we must have recourse to the 4th and 18th
Observations; from whence may be collected these particulars.

_Scarlets_, and other _reds_, _oranges_, and _yellows_, if they be pure
and intense, are most probably of the second order. Those of the first
and third order also may be pretty good; only the yellow of the first
order is faint, and the orange and red of the third Order have a great
Mixture of violet and blue.

There may be good _Greens_ of the fourth Order, but the purest are of
the third. And of this Order the green of all Vegetables seems to be,
partly by reason of the Intenseness of their Colours, and partly because
when they wither some of them turn to a greenish yellow, and others to a
more perfect yellow or orange, or perhaps to red, passing first through
all the aforesaid intermediate Colours. Which Changes seem to be
effected by the exhaling of the Moisture which may leave the tinging
Corpuscles more dense, and something augmented by the Accretion of the
oily and earthy Part of that Moisture. Now the green, without doubt, is
of the same Order with those Colours into which it changeth, because the
Changes are gradual, and those Colours, though usually not very full,
yet are often too full and lively to be of the fourth Order.

_Blues_ and _Purples_ may be either of the second or third Order, but
the best are of the third. Thus the Colour of Violets seems to be of
that Order, because their Syrup by acid Liquors turns red, and by
urinous and alcalizate turns green. For since it is of the Nature of
Acids to dissolve or attenuate, and of Alcalies to precipitate or
incrassate, if the Purple Colour of the Syrup was of the second Order,
an acid Liquor by attenuating its tinging Corpuscles would change it to
a red of the first Order, and an Alcali by incrassating them would
change it to a green of the second Order; which red and green,
especially the green, seem too imperfect to be the Colours produced by
these Changes. But if the said Purple be supposed of the third Order,
its Change to red of the second, and green of the third, may without any
Inconvenience be allow'd.

If there be found any Body of a deeper and less reddish Purple than that
of the Violets, its Colour most probably is of the second Order. But yet
there being no Body commonly known whose Colour is constantly more deep
than theirs, I have made use of their Name