"Monterey Mist" and "Light Tundra Metallic" are the same Ford color formula: 6D7676. In the RGB color model #6d7676 is comprised of 42.75% red, 46.27% green and 46.27% blue. In the HSL color space #6d7676 has a hue of 180°, 4% saturation and 45% lightness; color has an approximate wavelength of 491.41 nm.
This was an available color from 2003 to 2008 on Ford Taurus, Focus, F-series trucks, Freestyle, Five Hundred, Escape, Crown Victoria, Expedition, Crosstrainer, Freestar, Econoline Vans, Fusion and Thunderbird; Mercury Grand Marquis, Sable, Mountaineer, Monterey, Montego, and Milan; Lincoln Town Car, Navigator, LS, and Aviator.
Note that over time and exposure to the sun and other elements the actual color of your car's body may fade. So, a freshly painted fender or other body
part may not properly match the existing paint color/hue. Touch-up paints oft times do not 'perfectly' match the existing body paint, and it's even more pronounced in metallic finishes because it's necessary to match the flake size. Another issue is that touch-up paint is usually single-stage (
all-in-one) paint, whereas the body is two-stage paint (
basecoat/clearcoat). Application of metallic finishes (
air-pressure) can also affect the finished hue in metallic paint - it may look like a dead-on match from one angle but from another angle you can note the difference in hues.
A professional body shop would order the color based on the door code and/or use a spectrophotometer to identify the closest color match from a database of existing automotive colors and then manually add pigment(s) (
by eye) and do test spray-outs to get the color
matched.
It's more of an art than a science.