Because the screen medium is different from paper (emitting light vs reflecting light) pure black on white is a bit intense to the eye. General recommendation

Because the screen medium is different from paper (emitting light vs reflecting light) pure black on white is a bit intense to the eye. General recommendation is to reduce contrast a bit. A good starting point would be #444 for the text and #eee for the background. #eeeee6 would warm the background a tiny bit. Recommended line size is 65-85 characters, line-spacing at 1.3-1.5.