@GTatiana - It could be helpful if you were to tell us more about your set up – your device type/make and OS, are you connected to an external display, etc. Screenshots of what you are seeing may also help.

Sure! The problem is that I don't have the slider at all and I can not move the color palette, let alone adding new colors. I provide the screenshots. The first one is how it is supposed to work. The second is mine where you can see that I don't have any sliders.  I am also providing the link to the video of my screen where I am trying to move the color palette but there is just no slider and it won't go down - https://drive.google.com/file/d/1JFpXLyfCbkojdk6PO13fWrjx9omq-oD8/view?usp=share_link 

@GTatiana - Thanks for the video - this gets a little bit closer to understanding what might be happening. From the video, when I see the three coloured circles at the top left and I immediately think “mac” (although I have never used a mac). 

Is that Safari you are using? I also note something odd in that, although you have a Share button on your board and your picture/avatar, I also see a “Sign up for free” action:

Have you tired another browser or the Miro desktop app?