Hi @ costaricagal,
Welcome to the HP Forums!
I would like to take a moment and thank you for using this forum, it is a great place to find answers.
Do not worry I would be happy to help you with your HP Photosmart C4780 All-in-One Printer.
I understand that you are having scanner issue with your printer.
We need to first identify whether the issue is hardware or is it a software issue.
I also would like to know what happens when you make a color copy using the printer?
If you have not sure please make a color copy. Click on the link to know how to make a color copy.
If the color copy comes out fine please check the scan setting.
HP Easy Scan (Mac OS 10.9 and later)
Load the item on the scanner glass, in the document feeder slot, or in the automatic document feeder (ADF), depending on your printer type and features.
Search the Mac for a scan, then click HP Easy Scan in the list of results.
In HP Easy Scan, select your printer name from the Scanner drop-down menu.
Select your scan type from the Presets menu.
To change any basic settings to the preset you selected, such as scan color, orientation, or quality, click Edit Settings.
Click Scan.
Click Scan Next Item to add additional pages, or click Done.
Click the thumbnail version of the scanned item in the left panel. The item displays in the right preview pane.
Click Edit to adjust colors, straighten the scan, or crop the size.
To save your scans to a folder on the Mac, click Send in the bottom right corner of the window, then click Folder.
In the window that displays, click the Where menu to browse to the folder you want to save the file to, then click Save.
To view your scan, open the folder in which you saved the scan, then double-click the file.
Let me know how it goes.
Have a great day! ![Smiley Happy Smiley Happy]()