Are there any negative effects of samatha that were mentioned in the Pali Canon (Tripitaka), the commentaries, or just from your experience? I have heard on an occasion that someone who might concentrate on a color such as a blue kasina might end up only seeing everything in blue.
Summary: "Negative" is a subjective term - I believe there is learning to be had in every moment in life.
Certain Samatha and Vipassana experiences can puzzle the unstable or ignorant mind. The damage in these cases is self caused or self amplified.
I'm not saying one can be stuck seeing blue, but if one does, so what? Observe it too, like anything else, without a positive or negative attachment.
This mindset that wants some special experiences, and does not want other experiences is the real danger for any meditator.
Samatha jhanas and powers like any conditioned event are impermanent and will arise and pass away eventually. There is no wholesome joy to be had in special events in life - the wisdom is to be peaceful no matter what while developing the wisdom to know what is right and wrong.
There is not a lot of harm in curiosity, and some thrill seeking, but it comes at the cost of delay in the arising of wisdom.
It is ideal, though not always possible to have the tactical knowledge or a knowledgeable teacher at hand to guide one through some of these experiences. This ensures one does not compound errors in method.
If not that, then, developing an equanimous mind that is unattached to events is the best safety net.
Whether one is stuck in a sensation of bliss, or misery, the wise mind will remain unattached, unmoved, knowing it will all end.
Practiced correctly, there aren't many negative effects of samatha meditation. That being said, there are quite a few "detours" that one might stumble down without proper guidance. I think the greatest danger is bliss seeking and clinging to the bliss of jhana. From personal experience, I can tell you that this is particularly pernicious. Even knowing full well how easy it is to slip into this sort of thing, the highs that sitting can usher in are spectacularly enticing.
The subtle craving that the adsorptions engender (and sometimes they ain't even that subtle) really throw up a number of road blocks in your practice. For instance, you might start thinking sits where you don't get into jhana to be somehow "missed opportunities", you might start trying to reconstruct the feeling of absorption without letting it arise naturally, and perhaps most damaging, you start to think of enlightenment as this kind of blissed out alternative to samsara and not the resolution of form and emptiness as taught by the Buddha.
Jhana is Buddha, but pain in your legs is also Buddha. Almost feverish restlessness is every bit as important to your practice as ascending to the Brahma heavens. The danger is in distinction.