No, because otherwise there would be no verb. "Bluas" is a verb meaning (in this case) "is blue." If you wanted to use the adjective "blua" you would need to throw an "estas" ("is") into the sentence also.
Better because there is no rule that states that "verbifying" an adjective means "esti + adjective". Doing like such rule exist will make you sooner or later use an existing verb like "rapidi" thinking it means "esti rapida"