Thought it would be a good idea to start a 'Humbrol SAAF paint reference', the idea being that you post a picture of the subject to show the colours (so no misunderstandings!) and then pop in the Humbrol numbers that 'work' for you.
By no means the last word, these are some that I have used and have also been suggestions from others on this forum.
Mod: Use this site to convert between the various colour specs and model paint manufacturers:
The Ultimate Model Paint Conversion Chart What better way to start than with a classic Mirage IIICZ
Mirage IIICZ
Deep Buff; 63 Sand (may need up to 10% 34 White to tone it down)
Green; 75 Bronze Green
Admiralty Grey; 65 Aircraft Blue (may need 10-20% 34 White to tone it down)
Mirage F1AZ (late scheme)
Dark Brown; 29 Dark Earth
Dark Green; 30 Dark Green
Grey Blue undersides; 230 PRU blue (may need to tone it down with 34 White by 10-20%)
Canberra
PRU blue; 230 PRU Blue (may need to tone it down with 34 White by 10-20%)
Recently added courtesy of Dean (Bladerunner provided the Humbrol match);
Dark brown; 29 Dark Earth
Dark green; 30 Dark Green
'Cream'; 121 Pale Stone
Thanks to Dean and Bladerunner again
Nose/Radome: 127 Light Ghost Grey
Body/Overall; 128 US Compass Grey
'Diamond'; 125 US Dark Grey