So for H4 on the Projects sheet, you want to check the hours per month on the Hour Calculations sheet and based on its value, change the colour to either green, yellow or red.
we retrieve the hours per month value.
When this value is bigger then 136 you want to change the cell to red. So the first conditional formatting rule for H4 on the Projects sheet will be:
=VLOOKUP($H4,'Hours Calculations'!$A$4:$B$36,2,FALSE)>136 format cell as red.
Now do the same for the green and yellow colours.
Then drag H4 down as far as needed and click on the small square providing you with the option to "apply format only". This instead of applying format to each cell individually.
Does this yield the desired result?