All cedar will age out the same....at least all I have ever seen and being raised in the Northwest, I've seen a lot.
The important matching point here is if they are the same kind of shingles. Most cedar roofing is in the form of shakes, which are thickerr than shingles, and then heavy shakes (called 'heavies') that are thicker yet. Cedar shingles are usually not used on the roof, but are used as siding. If the two shingle (shake?) sizes are about the same the two roofs should lay down the same and will age in together, going from the cedar orange to cedar gray to a dark brown.
This has been my limited experience. Others may have more experience on this.