Highlight Cells based on a date in another column

[highlandranger]

I am trying to modify a planner to highlight a specific cell in a row based upon the value of another cell.

Here is an example of what I am trying to do. I want to be able to have the RED cell color based upon the Due Date.
sheetexample.jpg

The Puple Date Spread of each Project uses the following Conditional Formating: =AND(task_end>=K$5,task_start<L$5)

I would also like to alter this to ignore "weekends" when calculating Purple Date Spread for each project. Currently I'm manually editing these. But it would helpful if the sheet did it for me.

I have attached the sheet. Any help would be appreceated.