I will answer your question, but there is a much much much (320 much's) better way.
var text Red = "<font color=red>YES</font>";
IF(
[Related Candidate (ref) - Job Code] = "AACH25", $red,
[Related Candidate (ref) - Job Code] = "AACH41", $red,
[Related Candidate (ref) - Job Code] = "ADEV31", $red,
etc
[Related Candidate (ref) - Job Code] = "ADEV320", $red)
But the better way is to use excel to load up a table of these codes. Make the Key field of that table the code field. Add a formula checkbox field to the table called [Code exists?] with the formula of
true
Then using the [Related Candidate (ref) - Job Code] field on the right hand side of a new relationship to that Codes table, lookup the value for [Code exists?]
Then your formula would be simple:
IF([Code exists?], "<font color=red>YES</font>")
