What you can do is that you can edit a copy of the texture in an image making program like Paint.net.
First, make the area where the non-blue strands are black and the blue areas grey or white. If you want the blue area to be translucent (between opaque and transparent), choose grey. If you want it to be fully transparent, choose white. After you do that, save the image as a separate image file (I'll call it alpha.png).
Now go to Blender. Go to Cycles Render.
Then, go to the material's nodes in the Node Editor. Add an Image Texture node and load alpha.png in it. Connect its Color to a Transparent BSDF's Color. Then, add a Mix Shader node. In one Shader socket on the left side, put the Transparent BSDF. In the other, put the BSDF your actual texture (NOT alpha.png) is connected to. Finally, take the shader socket on the right side and connect to the Material Output.
Here's the explanation; connecting alpha.png to the Transparent BSDF creates something called an alpha. White means fully transparent, grey means between transparent and opaque (translucent) and black means opaque.