It's red.
I'd do plastisol, but if you have tones involved, pull the base back farther, double hit it (p/f/p/f),
and use the red as a mid-tone ( grey ) between the inks.
If you've got solids, whatever, it's a red shirt, you're fubar anyway.
Keep it tight, keep it smooth.
The white will be double hit, but that adds contrast to the black ink.
If you keep your ink right, it'll be fine.
Or whatever you figure works for you.
It's all good.
No matter what you do, don't overcook the shirts.
( red's a b*tch, lol )
Hope it works out.
Cheers.