Use photographs from live flowers and cut flowers to experiment with particular flower colors, types and shapes. As tulips are fairly simple shapes without too many petals, they are an easy flower to work with. The tulips in the photo above, are parts of living history. Both the narrow petaled viridiflora tulip and the wildly contrasting Silver Standard are varieties known to be grown in the 1700's which are still available today.
Avoid using flowers shown in period paintings unless you have alternate sources of comparison. One particular tulip flower appears in several paintings from the same period, often with plants that grow during several different seasons. That particular tulip was copied by many artists, although it flowered in that form only once, and is not necessarily drawn to life. It certainly would never have actually been available at the same time as the plants shown in the paintings, and recreations of painted floral arrangements of this type show a love for painting, but an ignorance of flowers. Period flower paintings were often not drawn from actual flower arrangements, but created to show off the valuable bank of floral material a prestigious collector or nursery might own.