Not intending to offend anyone. I have visited a few stately gardens here in the UK, where, basically this idea has been put into practice. Sections have been planted up with single coloured flowers. YUCK!
A garden bed or container planted in a limited colour palette can sometimes be very visually striking, but usually in my garden ecological benefit or botanical interest holds sway over pure aesthetics. I do seem to have a tendency to select plants with blue, purple or red flowers, but I also grow many plants with yellow, orange, pink, white, brown, and green flowers too.
At the moment I am doing my best to make a large bed with predominately white flowers dressed up a little with pink ones. I am finding that quite a challenge. It is one year in now from digging the grass out. I will persevere for another year (God willing) and see how it goes. It is a predominately shady bed with shallow and dry areas near trees.