Good hanging baskets with a bold statement can be achieved by using one type of plant in one colour.
Think about the volume of colour from your chosen flowers over the life of the hanging basket. Keep it simple and you will only need one watering and feeding regime.
The hanging baskets below generally fit into the single colour category with the odd liberty.

I like the powder blue Lobelia. It is far more stunning than the more traditional purple in this large hanging basket.

Petunias in purple, or would you call it mauve, are great for hanging baskets as they produce lots of flowers and self-deadhead.

I have not grown Bacopa but like the clean white colour scheme on this hanging basket.

Orange is an ususual clour for a hanging basket but there are now some brilliant begonias like these.
Begonia x tuberhybrida ‘Illumination Apricot Shades’ F1 Hybrid is fantastic but would produce a mix of yellow & orange.

Now we get to a cheat with a trailing Lysimachia to under pin the base of the hanging basket which contains red begonias.
Begonia from Thompson & Morgan

Is it fair to call this a single colour. Certainly this veined petunia in pink to purple makes a bold splash of colour.
Petunia Million Bells or Calibrachoa are very floriferous plants to try in hanging baskets.
Petunia seeds at Thompson & Morgan

This would be my hanging basket display of choice. Hydrangeas drink large volumes of water and would not normally feature in baskets but this USA garden at Longwood makes do.

Colour Photo Credits
Hanging Basket 2009 by amandabhslater CC BY-SA 2.0
Hanging Basket by sirwiseowl CC BY-NC-ND 2.0
Beautiful hanging baskets by wallygrom, CC BY-SA 2.0
petunias by NapaneeGal CC BY-NC 2.0
Hanging hydrangea hallway – Longwood Gardens, 2 May 2011 by mmwm CC BY-NC-ND 2.0
Cheerful pelargoniums by tsheko CC BY-NC 2.0

Cheerful pelargoniums