A close-up photograph tells you very little about the shrub you are buying. Flower colour is useful, but a plant with the right flowers can still be the wrong size or shape for a small garden.
Ask for the cultivar name and a photograph of the whole plant. Note whether the branches make a compact outline or a more open crown. Then check its likely mature size against the space available, including the width of a path beside it.
Compare plants at the same stage
Fresh flowers and ageing flowers do not always look the same colour. Shade, camera settings and a screen can exaggerate those differences. Compare open flowers in similar light, and use the nursery label to confirm what you are looking at.
Flowering frequency deserves a separate question. A name suggesting repeated bloom does not promise an unbroken display in every climate. Ask how that cultivar flowers locally rather than relying on a calendar from another country.
Before paying, write down the cultivar, expected size and reported flowering habit. Those three details are more useful than another close-up of the blooms.
Related reading: Osmanthus Variety Groups: Flowers, Leaves and Habit.