The 1/4" measurement is the outside diameter of the tubing and will work with all 1/4" Push-Connect fittings.
Red RO Tubing is used on most reverse osmosis systems to designate that the water flowing through it is unfiltered. On most reverse osmosis systems the red tubing will run from the source water connection through pre-filters and up to the source water input on the membrane. After the membrane the color of the tubing will usually change to blue to designate product water, and black to designate waste-water.
Sold in ten foot increments