How to shoot colourful photos
– Learn to recognize situations with great light that make colours pop.
– Avoid backlight, letting direct sunlight into the lens and dull light, such as overcast.
– Expose correctly: if your colourful subject is overexposed, it looks pale. Underexposed it looks grey and dull. Try to find the sweet spot inbetween. The image to the left shows the colour red (RGB=255,0,0) at different Lightness values in the HSL (hue-saturation-lightness) space: L=0 at the bottom 
produces black (underexposed) and L=255 at the top produces white (overexposed). The optimum lightness is found in the middle, at L=128, which produces the most saturated red. For example, exposing a backlit face for nice skin tones with a blue sky in the background will produce an over exposed white looking sky. Motives, where several objects with different colours have their sweet spot at the same exposure value, will produce several rich colours in the photograph, which may enhance each other to make the perception of colourful even stronger. Exposing a yellow facade in direct sunlight, with the sky in the background will produce a beautifully looking deep blue coloured sky in the photograph.
– Using complimentary colours or matching colour pairs (I like the combination of green and skin tones for example) in a photograph tend to enhance the perception of both colours.
– Change your cameras picture mode to Vivid (available even in most point-and-shoot cameras) or increase vibrance and saturation slightly in your RAW post processing. Warning: some puritans may think you are cheating.
Let me know what you think at colourful@photobysven.com
Stay curious and keep practicing! /Sven