The traditional color associated with a 25th anniversary (and, therefore, often used for a 25th birthday celebration) is silver.
This association stems from the tradition of marking wedding anniversaries. The 25th wedding anniversary is often referred to as the "silver anniversary," and this association has extended to the symbolic use of silver for other 25-year milestones, like a 25th birthday. The color represents the brightness, value, and lasting nature of a significant achievement or period. While there isn't necessarily one specific color required, silver is thematically relevant.
Therefore, if you are looking for a thematic color for a 25th birthday celebration, silver is a great choice.
