Flynn Rider vest details

Adding the details for the front of the vest has hit a snag. My plan was for the vertical lines to be simply stitches sewn down the vest, but as you can see it's practically invisible. You can see it somewhat in different light.

Here's a photo of the sample I did with different color thread and types of thread. The spool on the left is the color I'm using for general sewing. The spool on the right is the third color from the right on the swatch, next to it is a navy blue.

The thread on the 2 far right are with quilting thread. If I can find a thread color like the darker one I'll use that for the vertical top stitching.

You may ask why I don't double the fabric like the overlay. A double/triple layer would make the vest even hotter to wear, it's hard to say how hot it will be in Southern California for Halloween, it's been known to be in the 90's!