The most likely cause is a color-management/profile mismatch that shows up in that specific print mode. On Epson printers, different print settings and paper types can require different ICC/ICM profiles, and if the wrong profile is used, one mode can shift color even when another looks fine.

A second likely factor is the third-party continuous ink system. Epson’s driver/profiles are tuned for Epson inks and papers. If the aftermarket ink has different viscosity or surface tension, droplet formation can change—especially in modes like Photo RPM that may use different droplet behavior—so the printer lays down color differently than the profile expects. That can produce a cyan cast.

So the “why” is probably: Photo RPM uses a different ink/droplet/profile behavior, and your current paper/ink/profile combination isn’t calibrated for it.

Practical fixes:

• Check whether the problem occurs from all applications or only color-managed ones.
• Use the correct ICC profile for that exact printer setting and paper.
• Look for a custom profile from the CIS/ink vendor.
• Test with genuine Epson ink/paper to isolate whether the issue is the third-party ink or paper.