The caution fan stickers started in 1968. However, I think it's a nice touch. I have one on my 67. The grill color is a question better asked on the concourse fourum. I painted mine with Krylon 1613, then over sprayed a light coat of power steering teal blue to get a close match to the original.
There is no Caution Fan decal on 67s or 68s, and it's incorrect to have it on there. The decals were put on by dealers starting in 68, if a car came in for warranty or recall work. It was a Ford liability issue and the decals weren't put on at the factory.
The '66 grille blue color sold in spray bombs is a very close match. Lots of people on this forum could tell the difference, but non-Mustangers could not. I dusted my '67 grille with the '66 color and I can only see the difference in the two shades in the brightest of light.
Correct me if I'm wrong but I think you ment '65 grille not '66. The '66 I believe is black, but '65 is very close to '67. Some mustang vendors list the '65 grille paint.
Lucky for me several years ago I found a true NOS '67 grille in the gun metal blueish color.