This tool helps reduce ink totals in CMYK colors while keeping them visually unchanged. It uses Adobe Illustrator's default color profiles U.S. Web Coated (SWOP) v2 and sRGB IEC61966-2.1 to convert, compare, and generate clean, whole-number CMYK values with lower ink totals.
RGB Mode is designed for when you're building color palettes (like brand colors) and want to lock in solid CMYK values. Adobe Illustrator's default CMYK conversions often use more ink than necessary. With RGB Mode, you can optimize those values with virtually no visual change, even after your client has approved the colors.
CMYK Mode is for colors you've already printed. If you need to reprint with optimized values, this mode helps reduce ink while maintaining the look of the original. That said, your print shop likely has specialized tools for this and can probably batch-optimize your entire job more accurately, so just ask them.