I’ve added this metafield in my product page:
Is there any way I could change the background of the fields here; like white color.?
My client is not interested in paying for any app/extension. Is there any possible solution?
You cannot customize the native admin in that way.
The closest you can get is to have staff running a browser extension that enables Custom CSS,aka userstyles, for any website.
If these metafields are used in staff notifications then it may be possible to add style information to the email notification template.
https://help.shopify.com/en/manual/orders/notifications/order-notifications
And the process is similar if your intent is to color the background on the frontend of the website for customers.
Thanks for the response.
I ended up developing a simple browser extension to obtain the desired results for the time being.