In this support doc we explain where the colors you set in the "create order from" section are reflected on the actual order form.
The two color components on the create order-form page are:
1. Cart Theme Color
The cart theme color is placed in the header section and used for all titles of each individual element.
2. Purchase Button Colour
This color picker section gives you the ability to select the color of the "apply" button on the coupon code element and the order completion CTA button.