diff --git a/backend/app/core/captcha_image.py b/backend/app/core/captcha_image.py
index eb7c631..d6e0cd2 100644
--- a/backend/app/core/captcha_image.py
+++ b/backend/app/core/captcha_image.py
@@ -27,11 +27,12 @@ _WIDTH, _HEIGHT = 120, 40
 _FONT_SIZE = 25
 _PADDING = 8
 
-# 与前端配色呼应：墨色字符、青灰干扰、素纸底
-_INK = (15, 54, 70)
-_INTERFERENCE = (126, 156, 170)
-_SPECKLE = (168, 183, 192)
-_PAPER = (247, 246, 242)
+# 与前端 v3 配色呼应（--ys-ink / --ys-ink-2 / --ys-ink-3 / --ys-paper）：
+# 墨色字符、次级墨干扰、辅助墨噪点、纸白底
+_INK = (28, 35, 51)  # #1c2333
+_INTERFERENCE = (91, 101, 119)  # #5b6577
+_SPECKLE = (154, 163, 178)  # #9aa3b2
+_PAPER = (255, 255, 255)  # #ffffff
 
 _SPECKLE_COUNT = 46
 _INTERFERENCE_LINES = 2