Anyone aware of a suitable alternative for paint code 680? John

I believe the code 680 is infact the paint scheme code number and so I'd ask if the base colour is close to the Bermuda Blue of the 80's R and K's it's base code is 225 and schemes run on 644 and 645
Might be the same base colour therein.
Details found here http://www.bmbikes.co.uk/paintcodes/blues.htm

I think 270 is the color code not 680 which is the scheme.  I had a 16V K100RS in that color.  It is an entirely different shade from Bermuda Blue.  I think the official name for the color is Koenigs Blue.

Are you trying to get a match for existing paint?  If so, take a part and the 270/680 codes to a shop that supplies paint to repair shops. 

They will be able to get you a good match and may possibly be able to find the formula.  There is a shop near me that has been able to match Mystic Red, Pearl Silver, Pearlmut and Bermuda Blue.  It can take a little time to find the best match if they can't find the code in the book, so it's best to try to come by when they have some time to help you.

Thanks guys. still a bit confused. A UK website, https://www.bmbikes.org.uk/ucp.php?mode=login, shows scheme code 680/681, paint code 270, KOENIGS BLUE but the same website shows the colour for my bike 92 K75RT for that year as ROYAL BLUE METALIC 680 no paint code. 
Sadly touch up paint pens are no longer available.

If you just need a little bit to touch up chips you can try CycleColor.  The website takes a little time to figure out, but they claim to have all the proper color matches.  I bought some of their Mystic Red when I first got my K75RT and was very happy with the match.  They have a one ounce bottle with a brush in kits of base and clearcoat.

https://cyclecolor.com/

What are you looking to do? Color match or complete repaint?

Just looking for a colour match to touch up. Will have to take a side panel to a paint supplier.

Don't know what you have over there but here in the US the PPG paint matching computer does a fantastic job.

duck wrote:Don't know what you have over there but here in the US the PPG paint matching computer does a fantastic job.

+1  The guys I go to have a DuPont computer.