Can the background color of iphone6 SMS be changed?

This green is SMS, and the blue is iMessage, so you can't (jailbreak may have some themes).

Apple 6 SMS background can be set as a picture:

The steps are as follows:

1. Mobile phone jailbreak comes first.

2. Then download and install winterboard and Chinese package in cydia.

3. Install ifunbox on the computer.

4. Connect the mobile phone to the computer, open the ifunbox, and then create a new folder under the mobile phone/library/theme directory, which can be named arbitrarily. Name the required background picture (size 960X960, file format png) as SMSBackground@2x.png and send it to this folder.

5. Finally, check this folder in the mobile phone WB.