Toro Rosso are the final team to launch their car for the 2017 season.
The new Renault-powered machine was launched at the Circuit de Barcelona-Catalunya ahead of pre-season testing on Monday.
The STR12's livery is blue, red and silver, in a change from the traditional red, gold and dark blue.
"We really like the first major livery change of our 12 years on the F1 grid," team principle Franz Tost told formula1.com.
"Everyone in the team has worked extremely hard to ensure we have a very competitive season.
"Our chassis is mated to what is possibly the most competitive engine we have had so far in the hybrid era, as we return to Renault power once more."
Carlos Sainz will partner Daniil Kvyat, after Red Bull decided to retain him at their junior team having dropped him from the senior Red Bull squad.
BBC Sport chief F1 writer Andrew Benson
Silver forms part of Toro Rosso's eye-catching new livery, which seems appropriate as there is an essence of Mercedes about the design of the car, too.
The new STR12 - to be driven by the highly promising Carlos Sainz and the reprieved Daniil Kvyat - features a nose with a rounded end. Like the Mercedes.
And where its front suspension wishbone meets the wheel it is at the end of an arm of carbon-fibre bodywork that sweeps up from the wheel rim and in front of the tyre. Like the Mercedes.
At the rear, the swept bodywork in the so-called 'coke-bottle' shape between the rear wheels is heavily undercut in pursuit of optimum airflow, another impressive feature.
Together with the general neatness of the car, these underline the reputation of technical director James Key, who is widely believed to be on his way to Williams at the end of this season.
It looks like another effective car from the Red Bull junior team and regular points scores seem eminently achievable again.