Final answer:
The nurse should immediately notify the practitioner if a colostomy stoma is pale, as it may indicate inadequate blood supply, which requires prompt medical intervention.
Step-by-step explanation:
If a nurse identifies that a patient's colostomy stoma is pale, the first and most important action should be to notify the practitioner. A pale stoma can indicate inadequate blood supply, which is a significant concern that may require prompt medical intervention. The nurse should report this change in the patient's condition to ensure appropriate steps are taken to evaluate and manage the potential issue.
While other actions like listening for bowel sounds, washing the area with warm water, and gently massaging around the stoma might be components of routine stoma care, they do not immediately address the potential acute issue of compromised blood supply that a pale stoma suggests.