Boil potatoes with skin on in salted water until hilly cooked (about 15 minutes). Cool to room temperature, then remove skin. Set aside.
Blanch carrots, peas and red peppers in salt water until al dente. Chill immediately. Set aside.
Drain tuna; place on clean towel. Wring out excess water. Set aside.
Place potatoes in a large bowl and mash with a fork until all large chunks are gone. Add tuna, vegetables, eggs, mayonnaise and white pepper. Gently combine ingredients with large spoon. Add salt to taste. Place bowl in refrigerator to chill.