The best replacement for cyan is turquoise.

The best alternatives to cyan are rated as following:
★★★★★  turquoise
★★★★  teal
★★★  aqua
★★★  sabin
★★  cyan
★★  magenta
★  process blue
★  edgar
★  cerulean
★  black lumia 900
★  red blue
★  azure
★  tiffany blue
  galerina
  green magenta
  photo cyan

Your alternative for cyan is not listed? Suggest!
Speaking about cyan, one probably shouldn't forget about magenta.

Other search terms related to cyan and their ratings are:
★★★★★ magenta
You have in mind a companion for cyan and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of cyan in all years. Click on graph for more.
cyan
turquoise
teal