Here are some ideas for a party with a yellow colour theme
Yellow Decorations

Yellow tablecloth
Yellow napkins
Yellow candles
Posters with a yellow background such as a sunny beach scene
Yellow drapes
Daffodils
Forsythia
Yellow roses

Yellow Food

Yellow melon (cantaloupe melon)

Corn on the cob
Yellow pea soup
Bread made with wholeground cornmeal
Chicken tagine with preserved lemons
Sweetcorn
Polenta
Mung dahl
Banana split
Banana custard
Lemon meringue pie
Ripe golden delicious apples
Gouda and Emmental [...]

Related posts:

1. Red theme party ideas
2. Brown theme party ideas
3. Green theme party ideas

Source: Ideas Helper