Blue and yellow combinations should be avoided, given that many users (including the older adults and young’s) can suffer from tritanopia i.e. a visual defect that causes inability to discern blue and yellow.
Green and Red combination should also be avoided, once that many users can suffer from protanopia and deuteranopia, i.e. a visual defect that causes inability to perception of red and confusion of red with green.
Excluding the aspects mentioned before, the use of colors with long-wavelength end of spectrum (i.e. “warm” colors) are most perceptible than the use of short-wavelenghts (“cool” colors).