You shouldn't use CM's showroom for color sensitive purposes, its gamma is significantly different from AC so hue ends up way different. Within AC you'll probably have an even more extreme color error, something like that will go far more yellow. It's not missing red, it's just that a colour that starts as 100% red 10% green is being turned into 100% red 50% green
You could probably generate something like this to help use as a colour picker if you wanted... this is a full saturation rainbow in gimp, bottom half edited to have closer to AC's gamma.
What you see is the secondary colours (where you have 2 primaries mixing) cover significantly wider hue ranges. If you load this ingame and then clip it out so you can have it below the original, you could find the colour you want on the ingame version, then eyedropper it from the original.