What version of Premiere Elements are you using and on what computer operating system is it running?
Are you saying that when you open a project that you save closed that you are getting colorful Media Offline displays and also dialog "Where is the file.....?".
If so, that can have at least 2 causes
a. You have moved, deleted, or renamed file/folder for the source media that went into the project after you saved closed the project.
b. You are storing your source media on an external hard drive, and the external hard drive is malfunctioning (maybe drive letter changing).
You probably need to reconnect the project to its media by
a. Using the "Where is the file....?" message
b. Using the Replace Footage feature
The answers are in the details, and more details are necessary from you in order to help you troubleshoot this issue.