In the summer bedding geraniums and bedding begonias survive well without daily watering. Phormium look good in large pots and come in reds, yellows and greens
In the winter for colour, try large pots with a statement holly, Fatsia Japonica or Viburnum.
For your garden I’d suggest the Cranesbill geraniums, which are a semi shade loving perennial. There are loads of varieties, large and small, ranging from white through pink and blue to dark purple.
I you pick carefully there will alway be one in flower from spring to late Autumn. Some are evergreen.