the color will change. the multi years sticker was early in the program ( with different color having different requirement and overlapping expiration which they sorted out for the late years with extension via red.) and the current time frame / sticker color have a standardized qualitifcation and has a clear program scheduling with a clear ending date.
Current Clean Air Vehicle Decal | California Air Resources Board
specifically, it states that after january, the color is to be determined and that it will expired jan1, 2024 where for purple, it specifically states it will be valid only till jan 1 2023.
so it seems to me that the last decal color (jan 2022 and later) will be issue for multiple years all with less than 4 years of validity., ie, issue if you apply 2022, 2023 2024 and will all expire regardless in sep 2025 which mean eve if you get it jan1 2022, you will have 3 years 9 months of usage vs prior which is jan1 of the 4th years. and if you apply in june 2024 you will only get the usage for 15 months.
CAV Decals Issued on
Will be Valid Until
Decal Color
January 1, 2019 - December 31, 2019
January 1, 2023
Purple
January 1, 2020 or after to a vehicle that did not previously have a decal
January 1st of the fourth year of issue. For example, a decal issued on June 24, 2020 would expire on January 1, 2024
To be determined by DMV
January 1, 2022 or later
All decals expire on September 30, 2025
To be determined by DMV