No. Tá is a verb, and there is no verb in "The red hand", which is an lámh dhearg.
Note that lámh is a feminine noun, so the attributive adjective in an lámh dhearg is lenited. But predicative adjectives aren't affected, so the predicative adjective in Tá an lámh dearg is not lenited.
In English, attributive adjectives come before the noun - "the red hand", and predicative adjectives are in the predicate of the sentence, after the verb (and therefore, after the noun) - "the hand is red".