Libre Calc – color code a number of columns based on one column

I have a number of columns of data (one for each month) that I would like to color code based on the average value for all months. So each row in each column should be compared to the row in the ‘average’ column. I know vaguely how to use the conditional color scale formatting, but I can’t figure out what the formula is supposed to be so that I can apply it to all of the cells at once.

If the average value is in column BT, then the formulas need to be:

if row-x, column-y is less than row-x, column-BT

if row-x, column-y is greater than row-x, column-BT

spreadsheet