Assuming that
data starts in A2 going down,
"-" occurs in suffix only (i.e values are all of the format abab-suffix and not ab-ab-suffix)
Select data (A2:A1000) and conditional formatting>New rule>Formula
format as you wish. See attachmentFormula:
=MATCH("*"&MID(A2,1,FIND("-",A2&"-")-1)&"*", $A$1:$A1,0)
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