Ceylon SC 1-2 / Sg 2 And Blued Paper

Curious if anyone has any idea what the "blued paper" listed in Scott and SG means? If there is any sort of definition/description in either catalog, I certainly missed it.

At a guess, since the early issues were printed by Perkins Bacon, the blued paper may be due to the same cause as the blued paper found on their British 2d blues- a chemical reaction between potassium ferrocyanide used in sizing the paper and iron (III) oxide present in the ink. I'm guessing this produces Prussian blue (iron(III) ferrocyanide).

Otherwise it'ld be the use of pulp derived from cotton rags in the paper manufacture. Work clothes were commonly dyed blue, and if the rag pulp made from them wasn't bleached sufficiently the paper would have a blue tinge.

Well thank you for the explanation Flightle Bee. Looking to add those two stamps to my albums but obviously was asking as I'd have no idea what to look for versus the same stamps not on the "blue" paper.

There is a definite blue cast to the stamp. You don't need to look at the margins, which are often skimpy; you can see it in the image of the Queen. Ignoring the 1/2d value (which is a different case), you'll notice the difference when comparing to other values in the contemporaneous penny issue. The combination of time and dirt doesn't necessarily leave the other values "white" but they aren't going to have that blue cast.

ETA:
Here is an example of SG2b borrowed from Empire Philatelists: