To improve contrast in a logo that consists of several shades of blue, the most effective option would be adding a design element that is orange. Orange is a complementary color to blue, meaning it will provide a strong visual contrast, making the logo more appealing and easier to read.
Increasing or decreasing the font size may help with clarity, but it won't significantly enhance color contrast. Similarly, adding a design element that is longer than it is wide won't directly address the contrast issue. Therefore, the best choice is to add the orange design element.