Paving stones, some of them are a deeper colour to the rest

The white residue is usually left by the grouting material used in between the stones. Once the material is well set and dried out, you can use a jet washer to clean the grey-white layer. This should get you rid of your problem.

Yep some of the paving is likely to be more coloured then each other

Hi you need salt neutraliser before your slabs were laid they should of use a sealer that closes the pores it gets brushed on both sides before the slabs are laid It shows up especially on darker slabs You can buy salt neutraliser from most builders merchants This should help a lot

Could be slit colour differences on paks and the white colour is normally salt coming off the Blocks’s

Some of the best ways to remove efflorescence include: 1) Pressurized Water: Applying pressurized water may dissolve efflorescence quickly. If you use water, dry off the water from the building material after application. If you fail to remove the water, crystals may remain that can cause efflorescence to reappear. 2) Diluted Vinegar: If you’re in a pinch, using household diluted white vinegar can be used on efflorescence. It’s less harmful than industrial chemicals and you most likely already have vinegar in your kitchen. 3) Brushing: With a strong brush, you can remove efflorescence with ease. Removing efflorescence can be quick and simple. In fact, efflorescing salts are water-soluble, which means efflorescence may disappear on its own due to normal weathering. To clean efflorescence off brick, it is crucial to complete this task in warm, dry weather. At this point, moisture may bring additional salts to the surface of brick, and the salts can be removed by dry brushing.