I have two plants that I inherited in home purchase. I am not sure what type they are even but they do go into the greenhouse every winter with this winter being no different. I had an outbreak of scale across the citrus trees in the greenhouse where these plants were kept last winter so I'm sure sure if that is related but they came out looking like the attached pics. One is almost dead with white spots all over. The other has a more minor outbreak of something seemingly similar. Does anyone know if it is a fungus or insects (and what type?). What is the cure? Is there any hope of reviving these? Bonus question: what types of plants are these?

It looks like you have two things going on here, insect damage, and some other kind of damage, what kind I'm not sure, maybe cold damage? Or sun damage? In the pics it looks like mealy bugs, hard to tell from where the pics were taken. Neem oil for that, and it will take care of the scale, too. I'm thinking these are sago Palms?

Do you know if there is any hope for them coming back after treating with Neem Oil?

They might be cycads. I tried one in Florida. It attracted every mealybug and scale insect within a two mile radius. I could not control it and cycads do not tolerate sprays!
I gave up.

Do you know if there is any hope for them coming back after treating with Neem Oil?

It is bad in the sense that Neem Oil is one thing but the insects are so hard to control and they quickly get out of hand. I think that a good deal of yellow color comes from the fact that the juices are being sucked right out of the plant. Sucking the life out of it if you will.