Changing the color of your card is a feature available as part of Haystack for Business. You can check out all the extra benefits of Haystack for Business here: https://thehaystackapp.com/pricing
Note:
Haystack Cards using your work email might automatically receive a color based on your company brand (this is done by our Auto-Brand feature)
If your card features an old logo, you have the option to upload the new one manually via the 'card edit' screen in the app.