Quite a few years ago I designed the Chicago Bears field wall at Soldier Field. The print vendor, for some reason could not hit the Bears' official blue. It printed almost a purple. Of course the team rejected the entire stadium field wall. The printer had to eat the entire job and print it over again.
Another example was when we designed the Tostitos Fiesta Bowl in 2010. It was a complete re-brand. Tostitos had designed a new package for their tortilla chips and they wanted us to translate that to the stadium graphics for the National Championship Game in Phoenix. The packaging was mainly a navy blue but for the printer to print that dark blue on fabric I had to create graphic files with a baby blue in them. My files looked so "off", it was very nerve-racking.
When designing web graphics and web sites, color mistakes are forgiving. The designer can quickly upload revised files. Printing large-scale graphics need to be checked and checked again before going to production. The costs involved in printing, shipping, and most of all, installation can be in the tens of thousands of dollars.
I try to use PMS colors in my files. Printing a PMS color as a spot color versus a PMS color converted to CYMK can print dramatically different. Of course using RGB color in files will not print as seen on your computer screen since all the printing machines still using a CMYK process toy create the spectrum of colors. I have to be careful of the blacks in my files as well. A black created as C=0 M=0 Y=0 K=100 versus a black created with C=100 M=100 Y=100 K=100 prints much more like a true black.
Printing on vinyl mesh versus a 13 oz vinyl can create different colors as well. Because vinyl mesh as holes in it so air can pass through makes colors lighter. Less surface area to print on creates this. I usually go one shade darker as a rule to compensate for this.
I'm always creating graphics and effects in Photoshop and laying them over my Illustrator files. Using the same color in both programs sometimes does not get the same color value when printed because one is a vector and one is a raster (bitmap).
If I know I will be printing revised graphics for the same project in a year or two I will ask the printer to take note of the printer settings so when they go to print we get the same color results. It's amazing but even the temperature of the print shop at the time of printing can effect the color. I also make field wall panels no longer than 50 feet long because the color levels on the inkjet machine can also effect color and saturation.