Quick blurb from Tele-Tech:
Phosphors used in the cancelled RCA 19 inch color CRT.
EDIT: Short persistence red….
Interestingly, RCA increased the diameter of the holes in the center of the shadow mask and gradually smaller diameter shadow mask holes out to the edges of the cancelled 19 inch color CRT in 1954. That along with the phosphor changes were said by observers to give a noticeably brighter image and fixed the persistence problem.