Colors in Blocks-based Languages I am designing a blocks-based language to use in my classrooms and summer camps. Since I am using the Blockly framework, I am able to choose my own colors for the blocks and am looking for information to guide my selection. 

Personally, I find the number of colors in Scratch and Snap! and others to be overwhelming, and I hypothesize that young learners don't rely much on a block's color as much as its shape. But this is pure speculation—I welcome any reports from the front line or pointers to studies about block color.

Particularly, I'm interested in the method of grouping and organising the blocks into the color groups, rather than selecting the colors themselves: how should I select groups in order to help students understand each block's purpose? Are there any proven approaches of grouping certain types of blocks (e.g. flow control) together, or is the choice relatively arbitrary? Does the color choice have more of an impact than the shape and way of connecting blocks together?
Students use the colors for more than just interpreting the purpose of the block.  In my introductory classes, the color assists early-learners with locating the blocks within an extensive collection of choices.

When give a chunk of pre-existing code to recreate, a block's color helps communicate where in the collection to look for it.