I substituted at a school once where I needed to borrow colored pencils from another teacher to complete a project. She handed me a tub similar to the one pictured above full of colored pencils. She said that at the end of each school year she asks students to donate any unwanted color pencils to the box. She said you would be surprised how many you collect doing that.
She keeps the tub out when doing projects and students can borrow from it.
I did not do that last year (crazy year!) but will definitely do it this year to start my collection. While we require students to have colored pencils the reality is that they never have them when you need them.
As stated in an early post, colored pencils are preferred in the notebooks over markers (they bleed through) or crayons (wax makes it hard to write over it if you are taking notes or need to label something).
Occasionally I will need crayons and markers so I can see myself getting a few bins and having students donate those as well as pencils and red pens at the end of the year.
DISRUPTIVE STUDENT IDEA - I have a couple of early morning disruptive students in my homeroom class. They love to help and I actively look for jobs for them to do to keep them occupied or better yet out of the class :) I can see sharpening pencils (both plain and colored) might be a job I'll add to my list next year (I never let them use the electric one...too fast...they get the hand held pencil sharpener to slow down the work).