why do gray cells print yellow? black ink is 1/2 full

i am trying to print a spreadsheet where every other line is gray. the sheet cells are gray on my computer but when i print it, the cells are yellow or peach.

Gray is normally printed with colors NOT with black. One or two of your colors might be empty. Check your printer properties, there is normal an option to print gray with black ink. It might come out a bit grainy.