How to tweak RGB to CMYK conversion but leave other objects intact?
Level 3 PostScript has a powerful method for tweaking correction of device-dependent colors to device-independent colors: /UseCIEColor page device key and DefaultGray, DefaultRGB, DefaultCMYK color spaces. When UseCIEColor flag is on, grayscale, RGB, and CMYK colors are interpreted as the colors in DefaultGray, DefaultRGB, and DefaultCMYK color spaces. It is little known that an array form of device color spaces ( e.g. [DeviceCMYK]) can be defined as a Default* resource effectively disabling the corresponding conversion. Conversion of CMYK to device-independent colors is often undesirable because of the loss of black generation information.
