With a swivel-bladed vegetable peeler shred the carrots and cucumbers into fettuccine-like strands. In a large bowl whisk together the lemon juice and mustard. Add the olive oil in a slow stream while whisking constantly. Stir in sliced basil and red bell pepper. Season vinaigrette to taste with salt and pepper. Add the strands of carrots and cucumbers and toss to combine. Adjust seasoning if necessary.