The colours generally do appear though, except for the S stock. The subsurface lines are generally a bit confusing to newcomers though, Wimbleware should perhaps be split out or become part of the "Circle line" but there aren't enough different colours and they won't use dedicated stock
The interchangeable stock on much of the sub-surface Underground causes confusion for visitors, given that the line displays above the seats in many (all?) of the (non-Met) carriages alternate between District and Circle/H&C. I've several times had to help out people peering in a puzzled way at the line diagram in front of them if it doesn't seem to correlate with the journey/train they're on, and show them a different line diagram. I think this is a major problem with the mixing of rolling stock on these lines. The fact that the H&C diagram includes showing the Circle, but the District doesn't, means that correlating the two diagrams is difficult - though of course with the non-circular (in a topological sense) Circle now, that [adding the Circle to the District diagram] would add its own problems. I think that at least showing the Circle on the District diagram where the Circle shares tracks with the District might be helpful (ie from Edgware Road to Tower Hill, especially including the Earls Court "round the corner" connection), with the continuation just shown as a dotted line trailing off or something.
There have been times in the past when there were diagrams showing the H&C/Circle/District all on one diagram - though perhaps that ended up being a bit cramped. (Maybe it was in earlier rolling stock with a deeper space for the diagrams?) And there was also an era when the H&C/Circle diagrams included at least the "north-south" bit of the District, from Edgware Rd to Wimbledon.