What property to use in the instance theme to make the field darker?

[Elton2]

Hi everyone, how are you?!

The texts in the instance were in bold, so the customer asked to make it clearer.

I created a "UX Style" (img1):

{
"base": {
"text": "74, 80, 82"
},

"properties":{
"--now-unified-nav_header--background-color": "26,13,171",
"--now-form-field_placeholder--color": "text"
}

}

I associated it with "Theme" and it worked, but the borders of the fields on the forms are almost invisible. (img2)

Note: Would you know which "Property" I could use to make the edges more dark?

Thanks a lot 😉