I appreciate you trying the steps my colleague has provided, Eve. Having the option to add another column would be great, and I'd be glad to help you submit this idea to our product engineers.

Before submitting feedback, let's delete the custom field you've created:

1. In the Custom fields window, look for the custom field you created.
2. Click the Edit dropdown in the ACTIONS column.
3. Hit Make inactive.

Note that when you make a custom field inactive, this will be unavailable in all the sales forms.

Regarding your concern about adding another column, please note that this feature is currently unavailable. Thus, I encourage you to submit a feature request to our product engineers. They will review this and might consider it for future updates.

Here's how to submit a feedback within QBO:

1. Sign in to your QBO account.
2. Go to the Gear icon.
3. Select Feedback.
4. Enter your product suggestions.
5. Click Next to submit.

In the meantime, you might want to add the colors in the Description field as a word. Here's a visual reference:
 

You can also look for a third-party app to help you achieve your goal of adding a column to your invoices.

Moreover, you can check this article to create attractive, professional-looking invoices, estimates, and sales receipts: Customise invoices, estimates, and sales receipts in QuickBooks Online.

Furthermore, to receive and record invoice payments in QuickBooks Online, visit this article: Record invoice payments.

Your input is vital in shaping the future of QuickBooks. Let me know if you have other questions about managing sales forms, and I'll get back to you right away.