Clear monofilament is generally preferred as it doesn"t contain impurities that could interfere with its molecular structure. However, in certain conditions, coloured lines can be advantageous.
For example, green nylon fishing lines may blend well with vegetation or water with a greenish tint. Bright or fluorescent colours can improve line visibility for anglers, especially in low-light conditions or at night, helping them detect subtle bites or manage lines.
Ultimately, a colour choice often comes down to angler preference and confidence.