[Squidboy]

My guess was that the costumes were made with the color, but they soon found out that most of the colors would not show on-screen against the leather (note why the Orange/Gold and the Silver are brightest - because they are the furthest from black as you can get), so the costumes needed to be altered for the sequel, which is why many people thought the introduction of color happened from X2 onward, when it is clearly present from the start.