After looking at the comments and the votes, I believe that this question warrants a discussion. As I don't want to preference my own thinking above others in the community, I'll put my thoughts in an answer below.
I am perplexed about why this was closed in the first place, as I don't see how it can be a question about aesthetics at all.
Colors in a block-based language are an aspect of how organizing principles of code are communicated. A quick look at Snap! shows that these colors are not simply to be pretty, but rather to allow someone to easily be able to follow the flow of the code (yellow), or to permit a kid to easily spot why the pen is not writing properly (blue-green).
I haven't placed my vote yet, but I believe it should be re-opened (and I currently intend to cast my vote that way, unless some comment comes along here that I find persuasive). Perhaps others can explain why they believe it should be closed.
After a group discussion, we decided that we were unclear about OPs intentions, as there were multiple possible readings of the question. We discussed two possibilities:
- OP was asking about color choices specifically
- OP was asking about how to logically group commands by color in order to enhance student understanding.
In the case of (1), this question was deemed to be off-topic for cseducators, and a duplicate (or near duplicate) of this question from ux.SE. We believe that the question would possibly be on-topic at ux.
In the case of (2), then the question is on-topic for cseducators. It suffers from being unclear, however, and should be modified to make clear that it is about how to organize commands into color groups, at which time the question can be reopened.
I've been going back and forth on this question. I originally voted to close because I saw this less as a pedagogical discussion and more of a UX one. The design of an app for use in the classroom, while educational in the end, is initially about user experience; it just so happens that the users in this case are students. That fact doesn't necessarily make educators the experts. (I hope that makes sense: I'm trying to be nuanced.)
To explore this issue more, I went through UX.SE and found this question which has been viewed more than 10K times: Should software for 8 to 14 year olds be colourful and “childish”? (and which links to this bit of relevant research)
Based on those answers, which are informed by a deep understanding of color psychology and cognitive development, I see this as an area where UX expertise, as opposed to CSEd expertise, provides the better answer.
Maybe that's one way for us to draw a dividing line as we decide what's in and what's out here: is this the community with the greatest expertise on SE to answer that question? In this instance, I would have to say no.
To me this seems fairly clear cut: Is it a question about teaching computer science? It is, but it indirectly, and in my opinion, although I do really think it's an interesting question, it's too far from direct teaching to be on topic here.
I believe this to be too off topic because although it's a question about language design for a language used for teaching. You probably wouldn't call a professional language designer an educator (although some language designers are educators also). This is a language design and UX question because the core question is "How can I design a language for xyz (language design)? Which colors (UX design) should I use?" The goal of the OP is not to teach, but to design a language for use by teachers.
If questions indirectly related to computer science are made on topic for this site, I believe that we'd also have to permit questions like "How can I choose a UI design for my remote desktop tool for classrooms?" which sounds off topic to me.
The language design question is really asking about creating a tool for teachers rather than teaching and as such is off topic.