What kind of paint do you use to paint the grout between ceramic tiles

there is a grout color pen available..big box diy with first initial of...m it colors an seals the grout.

There are also color grouts. Check Lowes and other big boxer to see what's available.

https://www.tilecleaning.org/how-to-paint-grout-in-tile-floor.htm

I used a satin finish paint and sealed. My grout is white and looks great and no problem cleaning. Any color can be used or changed.

Try Grout colorant by Aqua Mix. It's an epoxy formula that provide better bonding to grout. Just google: Aqua Mix. They have a wide variety of colors and you can probably view the color chart at your local tile shops.

Definitely use something that is meant to bond to grout so it lasts longer and keeps it's nice look, especially on a well used place, like floors and bath surrounds

They have it at Lowes and Home Depot. I have done in my bath and kitchen . Both were to light and began to look dingy so I went to the store and found a small tube the color I felt would work. Came home and started in kitchen with old tooth brush and damp rag. Squeezed a line on area, then used toothbrush to fill and spread, wiped with rag and moved on. Took a while but was very satisfied, then when bath got dingy, when back to store and got color for that and started again. Liked doing it better because it was smaller but very pleased.

We used a grout pen, and It worked really well! You can see it here. https://alifeunfolding.com/updating-the-kitchen-in-our-rental-property/

I think you have all the answers you need to make a decision, It's really up to you to choose.