当我从Github导入项目时，我有两个在Xcode中显示为蓝色的文件夹，而其他所有文件夹均为黄色。怎么回事？

蓝色用于表示"文件夹参考"。

关于它们是什么以及何时使用它们的清晰描述来自http://struct.ca/2010/xcode-folder-references/

There are two types of folders in Xcode: groups and folder references.
You can use groups to organize files in your project without affecting
their structure on the actual file system. This is great for code,
because youa€?re only going to be working with your code in Xcode. On
the other hand, groups arena€?t very good for resource files.

On any reasonably complicated project, youa€?ll usually be dealing with
dozens a€" if not hundreds a€" of asset files, and those assets will need
to be modified and manipulated from outside of Xcode, either by you or
a designer. Putting all of your resource files in one flat folder is a
recipe for disaster. This is where folder references come in. They
allow you to organize your files into folders on your file system and
keep that same folder structure in Xcode.