looking for a column formula that will populate a value based on the values of two other columns

Hello,

I have a column that calculate the health color of a task (green, yellow, red, grey) using a formula and another column where the task manager manually input the color he believes is the actual health of the task. I would like to have a third column (which we will use for reporting) that will shown the value of the column manually input by the manager and if the values of that column are empty, use the values from the auto calculated column. Any simple formula that I can use on this third column? Thanks in advance.

Jose