Heat 2 teaspoons olive oil in a large nonstick skillet set over medium-high heat. Add red, orange and yellow bell pepper slices and cooking, stirring occasionally, until peppers starting to soften.
Add water and ¼ tsp salt. Cook until peppers are tender-crisp.
Remove peppers to a plate, tent with foil and keep warm.
Season salmon with ¼ tsp kosher salt and pepper.
Add remaining 1 tablespoon olive to the skillet, set over medium-high heat. Lay salmon fillets, skin side down, in the skillet and cook until the skin is crispy, about 3 minutes.
Turn over salmon fillets and cook for 2 minutes.
Turn salmon over so it is skin-side down again, spread 2 teaspoons pesto over the top of each fillet. Cover and cook until pesto is warm and salmon is just cooked through, about 1 minute.
Divide peppers between 4 plates and top with salmon fillets. Serve.