I don’t understand how I transfer the color palette value from screen2 to screen1?

Guys, I have a small problem. I don’t understand how to transfer the color palette value from screen2 to screen1

your block image is too low resolution.

and search 'start value' to see more posts about how to pass value between screens.

Simple. Use "virtual" screens (arrangements) instead. More memory friendly and better in other perceptions. Or you want to stick to the screens store the values in tiniDB.

The colour palette (Screen2) should absolutely be a Virtual Screen.

When we define virtual screens, we use one 'real' App Inventor Screen (most often Screen1). Screen-sized Vertical Arrangements on it are displayed/hidden as required - they are the Virtual Screens. This is generally a better approach for multi-screen Apps, they share data without having to "pass" it between screens and it also reduces code duplication, making the App more efficient and the code easier to follow if you have to return to it at a later date.

So, instead of separate "houses", virtual screens are "rooms" of the same "house".