Step 1Heat the oven to 425 degrees. Line a cookie sheet with foil and oil it lightly. With your fist, press the peppers gently to flatten them and place them on the cookie sheet skin side up. Brush with a little oil and roast until the peppers are tender and lightly charred, about 35 minutes. (Alternatively, grill the peppers or broil on low until tender.)
Step 2Transfer the peppers to a bowl, cover with plastic wrap and let stand for 15 minutes. Peel the peppers, return them to the bowl, and toss with the oil and vinegar.
Step 3To assemble the canapes, cut the peppers into 1-inch thick strips. Spread each toast lightly with mayonnaise and place a slice of egg and a slice of potato side by side slightly overlapping on each toast. Place a strip of green pepper and a strip of red pepper side by side along the length of the toast, trimming as necessary to fit. Top the red pepper strip with a white anchovy and the green with the brown anchovy. Repeat with the rest of the bread slices. Sprinkle the canapes with parsley and serve.