The Microsoft Windows standard API does not permit individual tabs to be disabled or locked. It is very unlikely that we would want to now move away from Windows standards in order to implement such a behaviour, given our enormous internal efforts to ensure that our software meets Windows standards. The Windows API also does not permit coloured tabs, so this feature will not be available in CAPITAL V8. (The tabs implemented in Series 7 are Windows non-standard.)
Because your second request would add significant complexity to the configuration of user screens and at best would only be used by a tiny fraction of the user base, it is unlikely that it would meet the criteria necessary to have it included in the standard package. You would be better off using the script functions SCRLock() and SCRHide() in conjunction with the function Security() plus other techniques, to implement a custom solution that would then do exactly what you wanted.