I've seen a lot of projects with this
How do you do that????
Each of the pair of arrows either increase or decrease a variable's (typically H, S, and B) value when tapped (or pressed). The texts that show "0" have a repeat forever loop to set their text to the value of the respective variables. Then in a drawing block, choose HSB for the color and instead of explicitly typing values, use the variables.
Try to learn by looking at the code in the project when you see something you're interested in. Then don't be afraid to ask for help if you can't figure it out but try yourself first. This will help you learn the code better and you can "play with the code" making changes to see if you understand it or help you figure it out. That's what remixing is all about.