Formula across multiple sheets

Edit your last post, then click Go Advanced. Select the paperclip icon, then Browse and upload the .xlsx.

See attached.

I started off by naming each range columns B:H in each sheet, I used the month abbreviations.

So go to Jan sheet, select B:H and type Jan in Name Box (just to left of Formula Bar). Repeat for each sheet with appropriate abbrev. name.

Then in Jul sheet, select column B and go to Home|Conditional Formatting|New Rule and select "use a formula to determine which cells to format"

Enter formula:

=AND(B1<>"New Joinees",VLOOKUP(B1,Apr,6,0)=0,VLOOKUP(B1,May,6,0)=0,VLOOKUP(B1,Jun,6,0)=0)

click Format and choose from Fill tab.

Repeat for other tabs.. with appropriate month names in formula.