Many of the pics on this blog and in our books get restorative treatment via Photoshop. As well as the inherent faults at the time a pic was taken such as high contrast or flatness and graininess, bad storage conditions for film can make things a whole lot worse with creeping crud and discoloration. Even the well-regarded Kodachrome wasn't immune to color shifts.
This is an example of an old slide often found in boxes in estate sales as the inheritors have zero interest in the subjects. A lot of editors wouldn't consider making use of something like this in the first place, however, historic interest can outweigh quality considerations.
The first step is to correct the angle -- here a rotation of about 2 degrees clockwise is needed.
The next step is to crop sufficient superfluous area to the right, to avoid detracting from the primary subject of the bus, although desolate areas like this can be useful for magazine spreads.
The next step is to restore colors, and that isn't as easy as it sounds as you need a good idea of what they should be and that requires reasonably accurate assumptions. The objective here should be to mitigate the "LA smog" effect, but not completely, as from the shadows it probably was taken in the late afternoon or early evening.
Areas of excessive shadow should be lightened a bit (but not a lot, the 'coal mine' appearance here was likely real) and little strange anomalies can be smoothed out or eliminated.
For a non-commercial blog like this, the level of processing below is sufficient, although for commercial purposes it would need more.