Regular flowers include:
Red, Yellow, and White Roses
Red, White, Yellow, and Purple Violets
Red, White, and Yellow Tulips
Red, White, and Yellow Lilies
Red, White, and Yellow Cosmos
Red and Pink Carnations (Received from your Mom and Dad on Mother's and Father's Day)
For Hybrids:
Pink Roses - Red+White, Yellow+Red, White+White, Pink+Pink
Purple Roses - White+White, Red+White, Purple+Purple
Orange Roses - Yellow+Red, Red+Red, Yellow+Yellow, Orange+Orange
Blue Roses - Step 1:
Use one of the following combinations to create "Hybrid Red Roses", or Red Roses that have an Orange and/or Purple parent.
Hybrid Red Rose = Orange and White Rose
Hybrid Red Rose = Orange and Purple Rose
Hybrid Red Rose = Red and Purple Rose
Step 2:
Create Blue Roses with one of the following combinations:
Hybrid Red Rose and Hybrid Red Rose
Orange Rose and Hybrid Red Rose
Blue and Blue Rose (Best combination) (information from Thonky.com)
Black Roses - Red+Red, Red+Orange, Red+Blue, Black+Black
Gold: Wait for a black to wilt, then water it with a golden watering can. The next day a gold rose should appear.
The rest you can find here:
http://http://www.thonky.com/animal-crossing-new-leaf/flowers-hybrids