Thank you for reaching out to us.

Indeed, mikveh on Saturday night is not an option for immersion this year because of Tisha B'Av. In this case, you should complete your clean days as planned and you can then switch to colored underwear on Saturday night. No bedikot are required on Sunday. 

Though the halachot of the nine days restricting bathing and grooming apply both before and right after the fast, preparations for mikveh are permissible because they are for a mitzva.

All mikveh preparations can be performed on Sunday night after the fast, but we recommend doing as much as possible on Friday, to take pressure off of Sunday night. For example, you could bathe and prepare your nails on Friday. On Sunday night after the fast and before mikveh, you should shower, wash and comb your hair, clean your teeth, and inspect yourself visually.

We also recommend checking mikveh hours and planning out the logistics in advance. Following Tisha B'Av, you can take a few moments for havdala and to grab a bite to eat (just brush your teeth well) before going to the mikveh.

We hope this goes smoothly. Please let us know if we can be of further assistance.