How to tell whether a (visual) design question is on-topic?

Question

This question is related to question about what is UX but goes more into details.

Comments on this question (Has this design got a name? (Overflow illustration out of web card)) got me thinking whether we have any guidelines on what visual design questions are considered on-topic. Visual design is a big part of user experience but which questions are better to be asked at Graphic Design SE? I know GD.SE and UX.SE do a lot of bleeding but how much visual design is too much for UX.SE?

Differences between UX.SE and GD.SE have been discussed for example in this answer to UI merging with GraphicDesign.

Answer 1

Generally, if the visual design aspect of the question is the core of it then it's off topic for here. However if visual design is just an aspect of the question then it may be suitable.

Think about the people in your office that you'd go to if you had that question - would you go to a graphic-designer first, or would you ask the UX person?

We care about the how's and why's of designs, whereas the something like that question is more concerned with the 'what'. If the question was about how that component functions (of which visuals are a part) then it'd be fine, but just asking what a style item is called isn't really a UX question at its core.

Really, it's easier to identify what isn't suitable to here than it is to define what is when it comes to visual / graphic design questions.