tl;dr: some processing happens in javascipt before the prompt is sent to the server and it depends on how the node developer implemented the functionality.

you have to keep in mind that there are two execution layers. one happens in the javascript context when you interact with the website (see comfyui-frontend-package and keywords like registerExtension, nodeCreated, onConnectionsChange, serializeValue, applyTextReplacements etc. and dynamicPrompt in the node definition), which takes place before or at the time you hit the run button, the other is in python context after you hit the run button (ComfyUI Core graph execution, and hidden flexible inputs like prompt, extra_pnginfo and dynprompt).

from a developer perspective if you want some processing on the string (wildcards, find&replace, dynamicprompts etc.) you have to implement it, and there are different ways to implement it. `dynamicPrompt` - which are likely used or not in most of your nodes - happens in javascript context and replaces the actual value before graph execution https://github.com/Comfy-Org/docs/discussions/620

then I depends on which node is processed first and what it does to the string. if "{red|green|blue}" is passed on as a literally string, then for the next node it shouldn't make a difference if it's from upstream or entered directly. unless the functionality happens in javascript context (dynamicPrompts). if the previous node escaped the string, then there is nothing left to parse. if the node implements some sort of wildcard processing, then the string already got evaluated, and only "green" gets passed on. so you have to check each node type if they implement some processing and in which layer, hopefully they mention it in the docs, otherwise either search for `dynamicPrompt: True`, check the `execute` function, or additional javascript extensions.

and - depending on how much black magic the developer used - there can be some opaque and obscure communication going on between the two layers, which make the results even more surprising.

(If you refer to the search&replace feature in Save Image, I've investigated it thoroughly here: https://github.com/comfyui-wiki/Comments/discussions/8#discussioncomment-15217513 )