[dfariswheel]

The 2 1/2" barrel models used the narrow "Service" type grips. The 4" and 6" used Target grips.
In those days the medallions would have been Silver. At the time, only the Python got Gold.
Later, Gold medallions began being used on all Colt's.

Here the "correct" type of Target grips for an early Diamondback.
Note the semi-circular checkering border under the medallions:

Here's the later type. These have a straight checkering border under the medallions.

 

[dfariswheel]

As just a general rule of thumb, the earlier the Colt grips, the darker the wood and the more figure.
You would see lighter, lesser figure Colt grips during any period, but in the later 1980's-early 1990's they really started getting lighter and will less figure.

 

[dfariswheel]

I think I commented on these somewhere else.
However........

The grips on the lower gun appear to have a nickel plated screw, which is wrong for a blued gun.
They do have the lighter, rather orange-blond color of later model grips.

BOTH grips appear to have just about zero grain figure, and I'm not certain these are in fact genuine Colt. Even in the later days, Colt grips were American Walnut and had a least some typical walnut grain, if not any figure.
I'd want to see these in person before making definite statements, but I'm wondering if these are Colt factory.
From the pictures, both appear to have that very non-grain look of a hardwood with a stain-finish over it.

"Usually" fake Colt grips have brass screws and screw bushings, usually on both sides, and genuine Colt have blued or nickel steel screws with a steel bushing only on the right grip.

In short, I'm just not sure about these.

 

[dfariswheel]

You sometimes find original Colt grips on Ebay, the gun auctions, and by posting a wanted ad on this forums Classified section.
You might have the best luck here.

For replica grips, no one I know of makes an even half way presentable replica.
There are the grips coming out of Asia, but they don't look very close.

Here's one set of replicas sold on Ebay. Sort of cheesy: