I also love the red color for my forms, Nithin8274!
You can change the color of the Standard template to red and your Packing slip will follow. On the other hand, were unable to change the Packing slip name since this form is not customisable.
Your question is tagged to QuickBooks Online for the UK, but it seems like you're not using the UK version. The packing slip in the UK version is already named as Delivery note, not Packing slip.
If you'll have more questions, just add them below.
