This video, uploaded June 25th 2015, appears to show two very different colored contrails, one described as "red" (although it's more of an orange pink, like a sunset cloud), and one "blue" (but really more like a normal white contrail).
The planes themselves are barely visible in the video, appearing only when reflections from the sun highlight a spot on the plane. There seems to be quite a long gap between the plane and when the contrail is first visible.
The two planes appear to be flying very similar routes, even appearing to curve in sync at one point (although it's not clear if that's a camera distortion). Regardless, they seem to be flying roughly together.
Here's a composite image of the two trails, focusing on a section of each that is the same distance from each plane:
Notice they are very similar in structure. But notice also when you look up close the "Blue" trail is not particularly blue - in fact it's pretty much white. It's also slightly brighter than the "red" trail.
There are three obvious reasons why two trails in the same sky might be different colors, in decreasing order of likelihood.
- Differing Illumination - If one trail is lit directly by the sun, but the other is not, or if one trail is higher than the other and the sun is low, then the trails can be different color (typically this is one trail being darker than the other.
- Differing Composition - contrails (like all clouds) get their color from a combination of reflected, scattered, transmitted, and refracted light. If one trail has smaller particles, or more particles, or different shaped ice particles than the other, then this can change the color of the trail.
- Differing Material - by far the least likely explanation - but if one trail was made of something different to the other (or contained some additional substance) then they would look different.
I'd not rule this out, but the similarity in size and shape of the trails seems to indicate they are two similar planes separated by a few thousand feet at most, and possibly even flying in formation at the same altitude. If this was a situation with a low sun, then I'd also expect the other clouds to be more apparently red.
Here are some examples of trails that are different colors near sunset/sunrise. Nothing that really resembles the video though.
The close up comparison of the trails then reminded me of this other Metabunk investigation of a red/blue pair of trails - this time inarguably at the same altitude.
The result of this investigation was one plane, with two different engine. The newer engine had a cooler exhaust, and so was producing a denser contrail with larger ice crystals. This meant that the color of the contrail was dominated by reflected white light.
The older engine had hotter exhaust, the resulting ice crystals had a shorter formation time (as the exhaust gas remained hot longer as it mixed with the ambient air), and so the trail was composed of much smaller particles, and so the color was dominated by scattered light, resulting in a different colored (and dimmer) trail.
So given this visual similarity, I'd suggest this is probably what is happening here with the red/blue trails. Two planes at similar altitudes, with one leaving a trail that has larger water particles than the other, probably because of different engines.