I'm not convinced the flowers are blue (in real life).
The VMS illustrator was working with a limited palette. Blue seems to me to be a fairly generic color for flowers and seeds. A symbolic way of expressing them. There is very little color mixing for flowers. The viola plant is a little more naturalistic, but attention to flower colors is somewhat minimal.
The "tidier painter" put quite a bit of attention into mixing greens for different leaf colors, but seems to have given less attention to flower colors.
The VMS illustrator was working with a limited palette. Blue seems to me to be a fairly generic color for flowers and seeds. A symbolic way of expressing them. There is very little color mixing for flowers. The viola plant is a little more naturalistic, but attention to flower colors is somewhat minimal.
The "tidier painter" put quite a bit of attention into mixing greens for different leaf colors, but seems to have given less attention to flower colors.