What kind of speciation has occurred in this example, and what has driven it?

Beetle pollinators of a particular plant are attracted to its flowers bright orange color. The beetles not only pollinate the flowers, but they mate while inside of the flowers. A mutant version of the plant with red flowers becomes more common with the passage of time. A particular variant of the beetle prefers the red flowers to the orange flowers. Over time, these two beetle variants diverge from each other to such an extent that interbreeding is no longer possible.
1. Allopatric speciation, ecological isolation
2. Sympatric speciation, habitat differentiation
3. Allopatric speciation, behavioral isolation
4. Sympatric speciation, sexual selection
5. Sympatric speciation, allopolyploidy