Word doesn't work with CMYK colours so Cyan is not simply interchangeable with Magenta.

Word's colours are RGB-based so each 'cyan' colour is going to be held in Word as a combination of RGB and hence need specific matching pairs to convert 100% cyan to its rgb equivalent to use in the find and then replace it with the target rgb value.

The solid cyan in your doc has RGB values of 0,174,239. The paler cyan is 225,244,253.

__________________
Andrew Lockton
Chrysalis Design, Melbourne Australia