You can add a background fill by adding a new fill below the pattern in the Appearance panel, you don’t need to change the pattern.
More info:
https://community.adobe.com/t5/illustrator/adding-background-colour-to-pattern-swatch/td-p/9367975?page=1
Tips, tricks and workarounds for design, media and technology
You can add a background fill by adding a new fill below the pattern in the Appearance panel, you don’t need to change the pattern.
More info:
https://community.adobe.com/t5/illustrator/adding-background-colour-to-pattern-swatch/td-p/9367975?page=1