Quite an expensive month with the issue of M20L code for the current top values in the shape of Special Delivery stamps for the <100g and <500g rates, the latter now getting a paler Queen's head and brighter fluor than an earlier issue. To be honest, the difference seems very minimal to me
Going back to 2019, here is an M19L edition of the 5p but in a deeper red shade of brownish-pink. again you may have trouble seeing much of a difference but the illustration at the foot of this post may help a little.
And then we have a few more 20 codes. The 1st Large Signed For is supposed to be a paler shade of flame red than last time. Once more, I am having a lot of trouble seeing these shade differences. It looks the same as the last one to me.
The next three are new 20 codes with no obvious further differences, although my new 99p UV torch does show how bright the backing paper is for the 2nd Class stamp!
Below are the new 5p (left) in the reddish shade and the previous browner shade.