According to the OED:
calyx n. The whorl of leaves (sepals), either separate or grown together, and usually green, forming the outer envelope in which the flower is enclosed while yet in the bud.
corolla n. The whorl of leaves (petals) either separate or grown together, forming the inner envelope of the flower, and generally its most conspicuous part; usually ‘coloured’ (i.e. not green), and of delicate texture. (Called by Grew the foliation. Cf. CALYX.)
Calyx and corolla, outer and inner, green and colored. Fascinating.