Direct verification of the completeness of the VIPERS colour selection as a function of redshift, using both VVDS-Deep and VVDS-Wide data, in W1 and W4 respectively. Note that the original colour criteria were defined based only on the VVDS-Deep data. The curves and points give the Colour Sampling Rate (CSR), i.e. the ratio of the number of galaxies satisfying the VIPERS criteria within a redshift bin and the total number of galaxies in that same bin. Both fields provide consistent selection functions, indicating that the colour–colour selection function is basically unity above z = 0.6 and can be consistently modelled in the transition region 0.4 <z< 0.6.