Indian sand stone

Don’t use cleaning products that might permanently discolour your sandstone! When cleaning sandstone paving slabs, it’s really important to avoid using anything that might permanently discolour the slabs. For example, any cleaning product that contains iron is likely to react with the sandstone and can produce a rust colour on the paving slabs. This looks awful and can be difficult to remove. Don’t do it! Similarly, many fungicides that remove lichens can permanently discolour the sandstone. Keep it simple Dirt, moss, and algae can usually be removed using a diluted mixture of household bleach. The bleach should not be used straight out of the bottle. Instead, dilute the bleach in a similar amount of water. Then pour the diluted bleach mixture onto the sandstone slabs and wait for 30 minutes. Then wash the bleach and contaminants away with plenty of water. The sodium hypochlorite (essentially, liquid chlorine) in the bleach kills the moss and algae, but it’s only a temporary solution; it won’t prevent a new infestation, so it’s important to repeat the process every few months or whenever you think cleaning is required, to keep your sandstone paving looking pristine. The lichen problem – just add a little elbow grease! While bleach is every sandstone paving owner’s best friend when it comes to dirt, algae and moss, it won’t destroy the majority of lichens. Instead, this is where a bit of elbow grease is needed.

You shouldn’t seal sandstone before laying, wrong slab has been used ! Natural stone doesn’t fade easily (looks different when wet) if taken care of

No if it’s decent quality sandstone then you don’t need use sealant for your slabs. You do however need to give them a good clean to keep them looking fresh through the years.

It sounds like you have had kandla grey sandstone laid. I think most grey sandstone will be a mix of different shades as it’s a natural product and is supposed to look like that. You can seal them and some will intensify the colour as they would look wet. As for should they have been sealed first. They could have been sealed first but don’t have to be. Some say that waiting until they have been laid for a few months to allow any residue to come up before sealing in the spring/summer when dry is better.

Unfortunately sandstone slabs are normally different shades. Only one I have used that’s not is the dark ‘black lime’ although I’ve stopped using that because it faded too quick for my liking and looked blue within a year. I wouldn’t say landscaper did a botched job or laid incorrectly from what you have said. It’s a natural product and can vary. If you seal it. It will enhance the colour and varied shades will be more prominent. Cleaning due to not liking colour is not an option unfortunately. You could try lifting the few slsbs you don’t like s and replacing them.