I don't think that the red color indicates that anything is bad about the partition; I think it is only Macrium color for that type of partition (in this case both your partition and the partition in the Macrium user guide are image partitions).
The option to change the size of the partition only occurs after you have selected that partition to clone and then in the destination disk you click on 'Cloned Partition Properties' to change the size (see page 142 of the User Guide). Clicking on the partition which I believe you did in the view of the Source disk will not allow you to change the size (because this is the original source of the partition you are trying to clone).
There's another red box partition on page 520 of the Macrium guide.
Still don't understand why these sections are in red? - colour of danger.
Windows 10 partition shows all blue - healthy.
Will clone the old C drive onto the new SSD.
Sorry - posts are crossing, probably while I am contending with Captcha.
There is nothing wrong with the C drive, it is mostly unused - will cone it to the SSD & update.
Have successfully cloned the old C drive to new SSD 'J' Drive.
How do I swap my old C disc, boot-drive to the new SSD drive please?
Do I need to go into BIOS & select the SSD as the boot drive
Can I physically remove the old C disc drive, & allow the PC to boot off the SSD, by default?
You did it correctly. Normally when cloning is completed you would shutdown the computer, disconnect the source drive, and connect the new drive. With a UEFI BIOS, if you leave both drives connected you would have to use the F12 Boot Menu to select the drive you wish to boot from.
If you wish to use your old HDD as additional storage, you have to reinitialize the drive. If you connect it to a SATA port you will have to boot using the F!2 Boot Menu to boot from the SSD. After booting from the SSD, you can use DiskPart to reinitialize the drive. Here is the procedure: https://macrorit.com/partition-magic-manager/initialize-disk-gpt-mbr-from-cmd-diskpart.html
Be careful that you select the correct disk to reinitialize. The 'list disk' command will list your disk drives and the 'select disk' command selects the drive to initialize.
Thanks, did not have to remove the GeForce bracket because one of the Sata ports ~ sata2 I think? - was available above it, just very fiddly to get the Sata plug plugged in. Will that GF bracket really come out by just removing it at the side of the pc - as shown in the manual - it is surely secured at the back of the case as well?
The old disc drive is still in there, minus Sata connection. I'd reformat it if I were to use it for storage.
"Will that GF bracket really come out by just removing it at the side of the pc - as shown in the manual - it is surely secured at the back of the case as well?" I don't have that model Dell so I don't know, but according to the the manual the bracket is not secured in the back.