I thought the alias was a shortcut or a substitute, not a replacement. Also I added the alias later on asI expanded my query and did not know why it was failing
Shortcut, yes. SUBSTITUTE, no. Once defined it must be used.
Remember that a table alias is not required IF the fields (many table or JOIN query) are all uniquely named. Also not required for ALL fields once defined. It's for making a field uniquely NAMED. (Especially helpful in self-joins.)
WHERE t.COL2 = t2.COL2
AND green <> red
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