CA depends on the lens, and its aperture (F-number). Low f-number means more CA, higher f-number is less CA. F-number above f12 starts to be softer and softer. On most lenses, f8 is close to optimal. CA is always two-colour, like purple and green or yellow and blue. One colour on one side, another on the other side.
If you take jpeg photos, you can press Info and turn On CA correction. This will digitally correct the CA of modern lenses. If you switch between Auto and M or other modes, this setting might change as well. Just go to Av mode, press Info, and turn on CA correction.
Secondly, it could be purple fringing. This is a purple line on high contrast edges, like when you have dark object in front of bright sky. CA also depends on aperture, but also on exposure. IF the photo is overexposed, very bright, then the CA will be more apparent. If the photo is darker (so the background is not pure white), then the CA will be less noticeable.
Wikipedia has good article on Chromatic Aberration and with many translations (left side, scroll down). Read "minimization" and "mitigation" chapters.
https://en.wikipedia.org/wiki/Chromatic_aberration https://en.wikipedia.org/wiki/Purple_fringing
Edit: Also, remember that most viewers don't notice this. This is something that photographers get obsessed with. But most audience does not care. You can buy lenses for $700+ if you want to have less CA. But even many $1000 lenses still have some
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