From time to time the question about correct blue and yellow in the Swedish national insignias is raised. Unfortunately it's a question with many answers.
During many years the national insignias were painted using masks. Yellow where first painted in a hollow circle, then blue and black were painted on top of each other using divided masks.
In addition to the fading of colour/paint the paint brand was also changed from Wedevåg (Swedens oldest company 1538 they delivered canons to the Wasa ship ) to other brands that might have effect giving slightly different appearance.
The picture of these Mustangs (from F21 Kallax/Luleå) shows a darker blue on the rearward aircraft. Except the explanations already mentioned, a darker blue colour was locally developed at F16 Uppsals for the blue outline of third squadrons yellow call signs (the yellow contrast against the bare metal/silver background was too poor). This darker blue colour may also have been used (accidently or indulgently) for the national insignias.
During the seventies, decals of the national insignias were produceed. This facilitated the appliance of the markings but also gave another source for slightly different shades of blue and yellow.
The somewhat odd diameters of the national insignias have their explanations in that the initial insignia had a design without the yellow border. The addition of 10% border on each side resulted in these peculiar sizes.
Please note that the design of the national insignia is not applicable for S 31 Spitfire, SWAFRAP AJSF 37 and TP101 ( it might be more).
In chosen colour in Moose Republic Decals however does not represent a brand new decal, rather a somewhat bleached. During the years of decal manufacturing different shades of yellow an d blue have been tried out and to mention some of the Pantone numbers used and the appearance of them.
PMS 123, consider sligthly too dark but might be closest match to a real 1:1 brand new insignia.
PMS 122, considered too bleached or pale.
PMS 116 same colour as the head of a Lego figure. This is considered to be an acceptable match of "mid" yellow tone.
PMS 300 is considered to be slightly too dark but might work in a model decal context if the blue is printed over yellow.
PMS 3005 is considered too cyan
PMS 285 has a mid blue tone, that might match the old painted (Azko Nobel paint) insignias better than a brand new decal used in the 80ies or the 90ies but is still a good model representation considering the scale effect as well.