Organisations on the Pro plan can customise the appearance of their embedded donation form to match their website's branding, including colours, fonts, and the thank you image. To see examples of customised forms, see What do embedded donation forms look like?
For customising all donation form settings (suggested amounts, donation frequencies, contact fields, custom questions, colours, and payment steps), see How do I customise my donation form? Changes made there apply to both the GiveNow cause page and the embedded form.