The cache is not hidden at the posted coordinates, just like the Flonase contribution to this series not found right around the corner from this one.
Is there no end to these library caches and all these puzzles involving the colors of the rainbow?
Not yet, anyway.
The color system you see below was developed by Andrew Lang over one hundred years ago (from 1889 to 1910). Try not to be put off by the oddity of the color coordination or the mathematical relations; at first glance it admittedly does appear rather muddled. I'll leave it to you to decide whether the result is an unsightly mess or something magical.
Crimson
Pink
Green
Blue - Violet
Orange
Green + Yellow
Brown/2
Violet
Red + Green
Yellow/2
Violet ± Lilac
Lilac + Green
Brown x 2
Blue - Orange
Violet - Grey
You can validate your puzzle solution with certitude.
Blue ribbons to toolrep1 for FTS and to tiptop3 for FTF.