@FNQGU mate, our industry finds 'black' is usually a bit cheaper than colours. Not as bad with injection moulding as MOQ's a very high. Rotational moulding 'black' is a good 'mould cleanout' colour yet best on UV stability. HDPE (High Density Polyethylene) floats whereas others like LLDPE and PVC mixtures sink when flooded. Maybe you could expand into Marine and or Military customers down the track with the right moulds from the start +100,000 runs as a good minimum maker guarantee mate!