Code to change button colour to white with black text

Store Design
1

store ( Blissbloom.shop )

Screenshot (5)
Screenshot (5)1366×768 225 KB

2

Hello There,

Go to Online Store > Themes > Actions > Edit Code > Assets > base.css
Paste your CSS at the bottom of base.css and click Save

.product-form__submit span {
    color: #fff!important;
}

image
image1346×494 150 KB

3

This didnt seem to work and also i would like the colours inverted