disk utility Partition icon greyed

Hello knwrk,

Thank you for using Apple Support Communities.

I see that you are looking to reformat a HD and use the GUID Partition Map. The following article addresses partitioning a disk and changing the partition map.

Disk Utility (El Capitan): Partition a physical disk

Particularly the following section:

Erase and repartition a device

You can erase all volumes on a device and create new ones. For example, if you want to change the partition map of a USB, Thunderbolt, or other storage device from Master Boot Record to GUID Partition Map. If you simply want to erase a volume, see Erase a volume.

WARNING: Erasing and partitioning a device destroys all data on all volumes of the device.

1. Select the device in the sidebar you want to erase and repartition, then click the Erase button .

   Note: You can’t erase the device that contains your startup volume.

2. Enter a name for the initial volume.

3. Click the Map pop-up menu, then choose a format for the initial partition.

   For MS-DOS and ExFAT partitions, the name must be eleven characters or less.

   • GUID Partition Map: Used for all Intel-based Mac computers.

   • Master Boot Record: Used for Windows partitions that will be formatted as MS-DOS (FAT) or ExFAT.

   • Apple Partition Map: Used for compatibility with older PowerPC-based Mac computers.

4. Click Erase, then click Done.

Best regards.

Hi knwrk,

At this point, you may find more information by using another one of Apple's support resources to help you sort out why it keeps asking for GUID scheme - https://getsupport.apple.com/GetproductgroupList.action.

Cheers