Orange/blue is not accessible for people with tritanopia. The only two-color scheme that works for people with all three types of single-cone-deficient color-blindnesses, is magenta/green. You can easily verify this with any decent colorblindness simulator.
The reason magenta/green works for all three, is that green is in the middle of the visual field, while magenta is a “fake” color (As in, there is no such thing as a “magenta” wavelength of light.) that is composed of equal parts red and blue, each which are at opposite edges of our visual spectrum. Someone with a deficient red cone (protanopia) will still see magenta as blue; someone with a deficient blue cone will still see magenta as red (tritanopia); and someone with a deficient green cone (deuteranopia) will still see the two as different hues, since green and red/blue are maximally distant.
As well, magenta/green is much easier for non-colorblind people to adjust to than orange/blue, as magenta/green is a strict superset of red/green (since magenta is by definition equal parts red and blue).
I figured this out a couple years ago by playing around with a color-blindness simulator until I found a color combination that worked for all 3 single-cone-deficient color-blindnesses. The explanation above as to why this is the case is original theory.