I am not the most sentimental guy but I think I understand this quote. A rainbow signifies two things:

• Sunlight in the clouded sky
• Color in the grayness of the sky

Both are possibly a source of happiness of and joy to people. What if we can the reason for somebodies happiness. How about if we are the reason for somebodies smile.

Consider how people react when they see a rainbow. Usually they just doing what they are just to enjoy the natures beauty. Maybe we can be somebodies reason for being this happy and enjoy life..........