Conditional Format Cell Color based on Two Other Cell Values Without Blank Cells Affecting

I have a maintenance task sheet based on hours in one column and days in another.
Each row contains the task followed by the hours and days due in their respective columns.

Some task are based on both hours and days due.
Some task are based on only hours due.
Some task are based on only days due.

I wish to change the font color of the TASK title in each row depending on the hours and days remaining. i.e.

If the Hours OR Days Due where less than or equal to 20 and 7 respectively color RED
If both Hours AND Days Due where more than 20 and 7 respectively color GREEN.
The color of the TASK based only on Hours or Days must NOT be affected by a Blank Cell

i.e.
A B C
TASK Hours Due Days Due
Oil Change 20 7 RED
Filter Change 21 8 GREEN
Brake Check 100 6 RED
Water Level 5 RED
Air Pressure 35 GREEN

So far I have conditional formatted the first column as below:
=AND(B2>20, C2>7). for the GREEN
=OR(B2<=20, C2<=7). for the RED

but get stuck on the NOT(ISBLANK).
As soon as I have either the Hours or Days Due cell blank the TASK goes RED.

Your kind input is greatly appreciated.

Ok, Please find attached file.

Below is the latest help I have received but does not allow an empty cell.

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I look forward to any assistance

Many Thanks.

I have cell C5 empty because It does not have Water Level checked based on Hours Due, only Days Due. This means the cell is left blank; so Water Level should be Red. On my spreadsheet it is Black.

Blank Cells should not cause a color change.

I hope that clarifys my problem?

I have also noticed that if I put a dash "-" in the empty cells for example it works properly but I don't want to have to put anything in the empty cells.

Yes, I have Thanks.

I have re-uploaded the file with changes to values in order to clarify my problem.

As you'll see, cells that are blank affect the color when they shouldn't; but cells with something in them other than numbers allow the sheet to work as desired.

I really don't want to have to put "XXX" or anything in the cells to get the correct color.

Thanks again for you patience

Hi,
I am still having problems with conditional formatting. Conditional Formatting using the built in Excel formatting seems to require very long formulas for what I wish to achieve. I was hoping to get some help coding with VBA instead.
I have attached a more exact example of my problem without adding the Excel Conditional Formatting. I have not been able to include the ISBLANK or NOT(ISBLANK) in all conditions due to lack of skill. I would appreciate any help arriving at a VBA solution. The columns with "TRUE" or "FALSE", only represent the formulas that I would use for the formatting. In reality they would be TASK's i.e. "Replace Oil Filter"