Why does the Raymarine display have green yellow shading

[tudorsailor]

I have a Raymarine C125 Multifunction Display using Navionics (or is it now Garmin) charts that are up to date. We are currently sailing around the Ionian. I have not knowingly changed any settings but on coming out the Meganissi channel the sea bed appeared to be shaded green. On zooming out I saw yellow and blue. I wondered if this was weather colours having sync'd with my phone but the shading persisted the next day when there was no wind.
WHats going on???
Thanks
Boyd (in Lefkas)