“6.2.3  An object shall be coloured to show a chequered pattern if it has essentially unbroken surfaces and its projection on any vertical plane equals or exceeds 4.5 m in both dimensions.  The pattern shall consist of rectangles of not less than 1.5 m and not more than 3 m on a side, the corners being of the darker colour. 

The colours of the pattern shall contrast each with the other and with the background against which they will be seen.  Orange and white or alternatively red and white shall be used, except where such colours merge with the background.”