At the long end of a zoom the centering alignment of the front element to the zooming elements and rear group is crucial, or you get an edge flare/softness off to one side. Pretty common for old zooms to end up with this kind of aberration.
At the long end the image circle is also at its largest, so the light exiting the rear of the lens is coning out and hitting the sensor at an angle at the edges (non-telecentric). Different sensors handle it differently, but it usually causes a bit of colour spread.
Out of curiosity I put an 8-64 on an Alexa and at 64mm there was noticeable colour fringing towards the edges of what would be a S16 frame. It shows up more if the centering/edge flare issue is also present. The fringing disappeared pretty quickly as I zoomed out. On projection the lens didn't show much CA at all.
There are plenty of good S16 zoom recommendations if you search the archives here, but the Canons (this one and 7-63) are often rated near the top of the pile.