Highlighting Differential Pairs in Altium

[electronx]

The PCB was designed, the gerbers were extracted in rs274x format. But it doesn't include the rs274-x2 version (so doesn't include differential pair impedance information). What can I do to highlight the differential pairs in Altium as below to show the manufacturer that some traces contain differential pairs?

[cearlobe]

Assign colours and generate plot using Net Classes and Differential Pair Classes maybe?

Normally diff pairs can be identified / selected in Gerber plots because their tracks will have (or can be made to have) unique widths, for instance use 0.145mm rather than 0.15mm.