Colour Coding and additional Security. The slip-on collet covers shown in this photograph prevent accidental removal or tampering with tubing. Tubing can be inserted with the collet cover already attached to the fittings or the cover can be slid into position afterwards. The cover is easily removed as and when required and comes in a variety of colours for colour-coding. Colours available - suffix iandicates colours i.e. E = Black, S = Grey, R = Red, B = Blue, Y = Yellow, G = Green. Please iandicate, by suffix the colour required or black will be supplied.