What a beautiful quilt! It appears that some of the triangles have 3 strips of color and some have only 2. It doesn't matter but I assume you want to be consistent. It looks like triangles cut from several strips of color. You could also add a strip of white fabric and then cut squares using the 45 degree line along the seam line between the color and white triangles.
Look at the Cozy Quilt Strip Tubing link below - it has the same HSTs you are trying to create.
http://www.createforless.com/Cozy-Qu...Feg-MgodURwAlA