“Nature is not always tricked in holiday attire, but the same scene which yesterday breathed perfume and glittered as for the frolic of the nymphs, is overspread with melancholy today. Nature always wears the colors of the spirit.”

History
Bartlett's Familiar Quotations, 10th ed. (1919), Essays, First Series
Variant: Nature is a mutable cloud which is always and never the same.

Source: War and Peace

Source: The Bed of Procrustes: Philosophical and Practical Aphorisms (2010), p. 19

Source: Eat, Pray, Love

Introduction, The Nature of Probability Theory, p. 6.
An Introduction To Probability Theory And Its Applications (Third Edition)

The Nightingale: A Conversation Poem, lines 13-22 (1798).
Context: "Most musical, most melancholy" bird!
A melancholy bird! Oh! idle thought!
In nature there is nothing melancholy.
But some night-wandering man, whose heart was pierced
With the remembrance of a grievous wrong,
Or slow distemper, or neglected love,
(And so, poor wretch! filled all things with himself,
And made all gentle sounds tell back the tale
Of his own sorrow) he, and such as he,
First named these notes a melancholy strain.

Source: The Chronoliths (2001), Chapter 13 (p. 156)