Plural or singular in lists

This probably has been asked before but I don't know exactly what good keywords are to search for an answer. I wonder if the plural form has to follow a list of descriptors.

Given the following sentences:

A) You will find screws in the red, green, and blue boxes.

and

B) You will find screws in the red, green, and blue box.

I tend to think that A) is the valid form because we talk about several boxes here, one red, one green, one blue. However, how would we know that there are not multiple red boxes? Equally confusing - would B) mean that there is one box, and it is red, green, and blue? Or is B) simply an invalid construct?

I am specifically interested in lists connected with "and". For "or", I found this thread which is imho reasonably answered.

Thank you for taking the time to read this.

Sentence B would mean that the is one box, colored red, green and blue (stripes perhaps). Sentence A means that there are multiple boxes. It does not indicate whether there is one of each color, or more than one box of some colors or all of the three colors. It implies that there is at last one box of each color. A list of descriptors joined by "and" implied multiple things described, and thus will use a plural form unless that implication is false, as in sentence B. A list of descriptors joined with "or" may imply only a single thing.

John lives in a red, green, or blue house.

Here there is only one house, and it is of only one color, but the speaker apparently is not sure what color it is.

Screws may be found in red or green boxes.

Here "or" is used, but there is apparently more than one box.

In short the form, plural or singular, is controlled not by the descriptors, but by what is being said or implied about the objects being described.

I think you're right - A is the correct thing to say if there is are three boxes, one of each color. B only makes sense if there is one box and it is multicolored - maybe it could be interpreted the other way, but the phrasing is awkward. You can change and to or to make the number of boxes more clear (as or implies a choice of one item from a list):

You will find screws in the red, green, or blue box.

To be more explicit you can repeat the word "box":

You will find screws in the red box, the green box, and (or) the blue box.

Or, to be more verbose but maybe even more clear:

You will find screws in any of the three boxes: the red one, the green one, or the blue one.

• Thank you for your reply. It is equally good as the chosen accepted answer, I think. Commented Jun 7, 2019 at 15:48