Wow, thanks for all your effort, Magnus! I didn't expect that ....
I've checked your suggestions concerning Valljo
70836 and
70879. That 836 for the upperside could fit but as I see from the webside 879 sure would not. It's far too brownish. Same is with Revell 75 Stonegrey, which I have here.
But I've checked my Vallejo boxes yesterday and found some other tones which could fit. First it's
71114 Medium Grey FS35237, which comes very close to the desired tone for the upperside. Then I found
71120 Dark Ghost Grey FS36320, which might be okay for the underside. Furthermore I found
71257 Lichtblau RLM 76 (new) 
which might also look good on the underside. But I'm still in favour for
71046 Pale Grey Blue FS36473 for the underside, which was also used for the older RLM 76 tone. Far too dark for the upperside in my opinion is
71273 Ocean Grey FS36176, which is even darker in my bottle than here on the monitor. I even found
Gunze H 308 Grey FS36375 in my paint box, which looks lighter than here on the screen.
I have all these paints here and this evening I made some test spraying on plastic spoons. I will take photos of that tomorrow in daylight and show them here. From the first view my favourite combination so far is Vallejo 71046 and 71114 or 71257 and 71114. Not sure yet ....
Thanks a lot, Magnus!
Torsten
Btw, there lies a Gripen Twin Seater kit here beside the Single Seater. I hope the SAAF colours are not too much different to the Swedish AF ones. I'm already checking. Otherwise I might go crazy ....