Sealing block paving

Anyone got advise on sealing a newly laid drive?
I have been advised to seal it but the sealer must contain polyurethane otherwise it's pointless doing it. Just worried it will spoil the look of the blocks. Any one done it?
Thanks

I did mine back before lock down. My blocks are a sort of light grey. They went significantly darker, a bit like the colour they go when it rains. They stayed like that for a few weeks but now seem to have lightened up again. I did use the polyurethane sealer so either it has worn off, unlikely, or I have just got used to it.

Thanks Pete,
I've got light grey blocks also. What sealer did you use? Thanks