My customer has opened the invoice but it is black, the only part they can read is the total. does this happen for other people or could it be something wrong at their end?

Hello there, pickbunjy-hotmai.

This might have something to do with a browser issue. It could be that the browser has stored too much cache, which makes the invoice appears as black.

We can let them refresh their browser by clicking the Reload icon or pressing F5 on the keyboard. If it's still showing as black, we can do some troubleshooting steps to fix it. Advise them to open the invoice through an incognito window. Here's how:

• Google Chrome: Ctrl + Shift + N
• Microsoft Edge: Ctrl + Shift + P
• Firefox: Ctrl + Shift + P
• Safari: Command + Shift + N

If it works, go back to your main browser and clear the cache. It'll remove any browser-related issues and refresh your browser's settings. Another way that you can share with them is to use compatible browsers in QuickBooks Online. Below are the supported browsers with QuickBooks: 

• Mozilla
• Google Chrome
• Microsoft Edge
• For Safari, make sure to use the latest one.

Also, you can change the invoice design the way how you want it to send to your customer, but it only highlights the invoice details and customer's name, excluding the total. You can change it by selecting another color. Here's the sample screenshot:

Lastly, you can check the articles below  for additional information about managing invoices and categorising transactions in QBSE: 
 

• Set up your invoice preferences. 
• Learn how to keep your transactions organized. 

Let me know if you have other questions. I'll be right here to help you anytime. Take care always.