Finding synonyms for the phrase "nailing colors mast" requires a bit of creativity, as it is a somewhat obscure idiom. One possible synonym could be "staking a claim," as both phrases suggest a strong and unwavering commitment to a particular cause or belief. Another option might be "asserting oneself," which conveys a similar sense of confidence and determination. Alternatively, one could use more literal language to describe the act of displaying a flag or banner, such as "hoisting one's standard" or "raising one's flag." Ultimately, the choice of synonym will depend on the context and tone of the piece of writing or conversation in which it is being used.