A front-door mat should trap dirt, resist slipping, drain or dry properly, fit the threshold, and remain visible in the entrance lighting.
Quick answer
Choose colour after material, size, contrast, weather exposure, accessibility, and door clearance have been resolved.
Fit the mat to the doorway
The door must open freely and the mat should not curl, slide, or create a trip edge. Check the surface when wet as well as dry.
Use colour with the whole entrance
Door paint, paving, wall finish, and lighting change how a colour appears. Five-phase colour associations are optional cultural context, not a performance rule.
Maintain the boundary
Shake, wash, or replace the mat before it becomes saturated or damaged. A clean safe threshold supports daily use more directly than a promised lucky colour.
Boundary: Feng shui is a cultural and design perspective. It cannot guarantee health, wealth, relationships, safety, or other outcomes. Use qualified professional advice for building, electrical, plumbing, fire-safety, accessibility, horticultural, or medical questions.