The Victoria Stroop Test (VST) is a test of cognitive flexibility and inhibition, both executive functions.
The test is in the public domain and can be accessed through texts such as as Strauss, Sherman, & Spreen (2006).
Subscribers to NeuropsychologySA can access the test, including the stimulus cards and instructions for administration and scoring here.
Strauss, E. S., Sherman, E. M., & Spreen, O. (2006). A Compendium of Neuropsychological Tests: Administration, Norms, and Commentary. Oxford: Oxford University Press.