Formula to detect if a number is used at least 3 times but not more than 3

[addison99]

I currently make my shift rota in excel but need to try and create some formulas to ensure I dont make mistakes

we have 3 shifts at the business and each shift needs to have 3 employees we currently have a spread sheet and use 1 2 3 to indicate which shift they will be working, while this is working okay mistakes are happening. something like shown below

Date Employee 1 Employee 2 Employee 3 Employee 4 Employee 5 Employee 6
1 2 1 2 2 3 2 3 1 3 off


What I would like to do is to ensure I have the staffing correct the numbers will change green but if I dont have the staffing correct the numbers will go red, hope this makes sense.

[Gregb11]

Can you upload a sample file with expected results?