"render more colourful and lively" [OED], 1966 (the year of "Time Has Come Today" by the Chambers Brothers), from psychedelic + -ize. Related: Psychedelicized; psychedelicizing.
Entries linking to psychedelicize
psychedelic adj.
occasionally psychodelic, "producing expanded consciousness through heightened awareness and feeling," 1956, of drugs, suggested by British-born Canadian psychiatrist Humphry Osmond in a letter to Aldous Huxley and used by Osmond in a scientific paper published the next year; from Greek psykhē "mind" (see psyche) + dēloun "make visible, reveal" (from dēlos "visible, clear," from PIE root *dyeu- "to shine").
In popular use from 1965 with reference to anything producing effects or sensations similar to the common perception of the effects of a psychedelic drug. As a noun, "a psychedelic drug," from 1956.
-ize
word-forming element used to make verbs, Middle English -isen, from Old French -iser/-izer, from Late Latin -izare, from Greek -izein, a verb-forming element denoting the doing of the noun or adjective to which it is attached.
The variation of -ize and -ise began in Old French and Middle English, perhaps aided by a few words (such as surprise, see below) where the ending is French or Latin, not Greek. With the classical revival, English partially reverted to the correct Greek -z- spelling from late 16c. But the 1694 edition of the authoritative French Academy dictionary standardized the spellings as -s-, which influenced English.
In Britain, despite the opposition to it (at least formerly) of OED, Encyclopaedia Britannica, the Times of London, and Fowler, -ise remains dominant. Fowler thinks this is to avoid the difficulty of remembering the short list of common words not from Greek which must be spelled with an -s- (such as advertise, devise, surprise). American English has always favored -ize. The spelling variation involves about 200 English verbs.