Multiple condition, multiple range formating

In range C15:C45 I have names of some steps. Starting from column D, row 6 have a drop down with 6 possibilities. Now based on what is selected in row 6 (so cell D6, E6, F6 and so on), I would like to color certain cells from 15 to 45 in that particular column (certain steps that are applicable to option selected in row 6 of that column). And as month goes by, users do that in more and more columns.
Also, steps overlap between conditions that are selected in row 6 and I would like this to macro (or formulae) to be running so that as soon as user selects the condition cells are colored and then they can fill out only those cells.

So, I couldn't figure out any way to do this by conditional formating as there are more than three conditions and range is not continuous.Please see attached file as an example of final output.

Any help would be greatly appreciated.

Thank you in advance,
Jay