This is normal practice. To publish in a respectable journal you are charged £1000+. To publish your paper as open access, you can be charged another ~£1000 for the privledge (IEEE).
Depends on the field. For example, practically all of machine learning and related fields are $0 to publish and are open access by default. It’s been a huge boon for everyone except I guess traditional publishers.
And I see all these people cautioning against publishing in predatory journals, which can be distinguished by the fact they require me to pay to publish. Then we have the big respectable journals which also require payment to publish. Hmm...sounds like the only real difference is the respectable journals are considered respectable and the predatory journals are considered predatory...
No. If you want to submit color regardless of medium.
Besides, color printing isn't that costly compared to their high margins. It's in their favor too if people use color images, the age of simple scatterplots has passed for most fields.
In my area of semiconductor engineering/ detectors, we generally have to pay to publish. Journals do seem to be slowly moving away from this for just the publication, however as you say for open access you still need to pay. Depending on the funding provider for the research, it can be compulsory for the papers to be open access, so we would end up paying anyway.