Out of gamut colors in vector images

What @Abambo said. And, of course, except possibly for very specialized printing processes and the types of paper used, printed colors will not look as bright as they do on screen. Those are adjustments our brains need to make on the fly. Images viewed by reflected light are seldom a match for those viewed by transmitted light.

That's an eternal problem. It depends on the skill and the possibilities of the buyer if they can handle that. And they will need to make tradeoffs. So either you supply assets completly in line of the limited CMYK gamut, or you ignore that, and hope that the buyer knows what they do. There is no magical solution to this, unfortunately.