Dan, not to interrupt your current question of the moment. But, regarding color choices, that came up elsewhere & I'll reiterate what I posted here just for your general info....
IMO, people tend to overthink it. Especially with tending to be too careful with regard to color blindness. Which is a subject that seems to always come up.
"Color Blind" is a misleading term. Total color blindness is extremely rare. Something that effects only about 1% of those who are deemed "color blind". The other 99% are more correctly "color deficient". & that color deficiency runs the gamut from very slight, to moderate, to strong, before finally getting to that final 1% at absolute.
In terms of percentages, about 8% of men are some form of color deficient, while among women that figure is roughly 0.5%. So, population as a whole, around 4.5%. While not an insignificant number, if you roll all this up, severe to total color blindness becomes a fraction of a percent.
Also, far and away the most common color deficiency (effecting nearly 99% of all color deficient) is a degree of red-green blindness. Now, it's not that this person can't see a difference between red & green, (which is also confusing to the non-color blind) but rather detecting between various hues of reds & greens. These are actually two different deficiencies that are confusingly limped into one "category". One is red deficient, the other is green deficient.
My 1st wife was one of those rare females with this problem (Protanopia - red deficient). These charts will help the non-color blind understand it some. The normal color spectrum most of us see is on top, while the way the color deficient person sees it is on the bottom.
Even to a red or green deficient person a red/green combo would still be fine, it's a green/orange combo that might present a problem to one. & a green/yellow combo could be an issue to the other, depending on the shade of green used. Red/orange would obviously be an issue for both.
Now, if you're really intent on pairing colors based on that, it's not that difficult... take your basic "color wheel", based on whatever color you might be starting with. the 2 colors that are at least 90 degrees from that color are your other two "working points", with those & anything between them being a "safe choice".
So, if yellow is one deck, blue-green & red-orange would be your other two points, with anything between also being a safe choice.
Now, while I'm currently a Shuffletech owner & my interest in bridge size cards has dropped from slim to none, I will add that I am so tired of red/blue as a combination I avoid if at all possible. To the point where if I can get a second set that is not red/blue I'll get a second set just so I can split the red/blue set up & pair 'em with a different color.
Yea, I'm THAT tired of red & blue as a combination.