There are multiple different color spaces that have different degrees of vibrance for RGB and in-between.

sRGB uses 256 shades per color. So while this totals >16M combos, if you want a shade of red to be 137.5, you’ll have to settle for 137 or 138.

Also, printers use ink, not light, and are using CMYK (K is for black, not used a lot in standard colors, moreso metallic and gold-ish). CMYK can go more vibrant for green but less so for blue/purple. It uses 0-100 for all 4, totaling 104M combos.

Printer calibration is a huge issue. My mother uses Walmart for Christmas photos and every time they look like crap. A huge benefit of Pantone is that print shops order Pantone books of swatches (stupid expensive) and they calibrate their printers are accurate, so if your digital file is using a specific Pantone color, then that is exactly was is getting printed.

Now, some shops give out their ICC profiles and you can download them it’ll show you what your image will look like from that printer. However, you are still looking at it from a digital screen emitting light and not a printed surface reflecting light.