Thanks for your mail and for purchasing Colors! 3D.
Unfortunately, there is no way to circumvent this requirement in the tutorial. When Colors! 3D was released there was no 2DS so the problem surfaced only after Nintendo released a console without the slider.
On the bright side though, the tutorial is very basic and I am sure you will get the hang of all the features of the game rapidly just by playing around with it. Also, a good source for help and inspiration is the #tutorial tag on the Colors Gallery (you can find it in the game and on colorslive.com). You are also welcome to join our Discord Server where you can chat with us developers and many helpful users. You can join here: colorslive.com/discord.
We are working on some exciting new stuff for Colors! so keep an eye out for updates at Discord and in the News feed in the Gallery (which you can find in the game).
Hope that covers most of it. Can I help you with anything else?