Hi @samanthag,
Welcome to the Bunnings Workshop community, it is wonderful to have you with us.
Regrouting your tiles starts with removing the old grout. Check out How To Remove Grout From Tiles for some guidance on this step. You'll need a grout removal tool, such as a grout saw and a vacuum cleaner.
Once the grout has been removed, you will apply new grout to the lines. There are a variety of different coloured grouts that you can choose from. Check out the range of Dunlop Flexible Coloured Grouts for premixed options and Davco Sanitized Colourgrout for powdered options that will require mixing.
Once you've selected a grout colour that you are happy with, follow How To Grout Tiles for some guidance on the process. You'll need a Grout Float to apply the grout, a sponge to clean up and some buckets for water and holding your grout if you are mixing it.
Although not 100% necessary, a good pair of knee pads will also come in handy.
Let me know if you have any further questions.
Jacob
