I am trying to make a spreadsheet that when a numbered cell in one column is
used in a second column, that the cell in the first column becomes filled
with color.

Example: I have cells in Column "A" numbered from 1 to 10. In column "C" I
have cells that can be filled with numbers. When I, for example, put the
number 3 in cell C1, then cell A3 would become colorized. When I, for
example, put then number 1 in cell C5, then cell A1 would become colorized.
etc., etc..

Can anyone help?