The Collaborative International Dictionary of English v.0.48:

Unfading \Unfading\
   See fading.

WordNet (r) 3.0 (2006):

unfading
    adj 1: of an imaginary flower that never fades [syn:
           amaranthine, unfading]

Moby Thesaurus II by Grady Ward, 1.0:

83 Moby Thesaurus words for "unfading":
   abiding, age-long, aged, amaranthine, ancient, antique, changeless,
   chronic, colorfast, constant, continuing, deathless, deep-dyed,
   diuturnal, double-dyed, durable, dyed-in-the-wool, embalmed,
   enduring, ever-fresh, evergreen, everlasting, fadeless, fast, firm,
   fixed, frozen, hardy, immobile, immortal, immutable, imperishable,
   incorruptible, indelible, ingrain, ingrained, intact, intransient,
   inveterate, inviolate, lasting, long-lasting, long-lived,
   long-standing, long-term, longeval, longevous, macrobiotic,
   never-dying, of long duration, of long standing, perdurable,
   perduring, perennial, permanent, perpetual, persistent, persisting,
   quiescent, remaining, rigid, sempervirent, solid, stable, static,
   stationary, staying, steadfast, sustained, torpid, tough,
   unaltered, unchangeable, unchanged, unchanging, unchecked,
   undestroyed, undying, unfailing, unshifting, unvaried, unvarying,
   vital