窃谓脉之理微。色之理愈微。盖有可以意会。难以言传者。然病症不同。气色当异。苟推而广之。扩而充之。
触类而长之。则虽难以形容者。亦可以拟议焉。如风色当青。寒色当黑。暑色当赤。湿色当黄。风令脉缓。寒
令脉急。暑令脉虚。湿令脉涩。脉缓者。尺之皮肤亦缓。脉急者。尺之皮肤亦急。脉滑者。尺之皮肤亦滑。脉涩
者。尺之皮肤亦涩。脉大者。尺之皮肤亦贲而起。脉小者。尺之皮肤亦减而少气。合色脉皮肤而参观。则风
令脉缓者。当色青而皮肤缓。寒令脉急者。当色黑而皮肤急。暑令脉虚者。当色赤而皮肤减而少气。湿令
脉涩者。当色黄而皮肤涩。夫如是而风寒暑湿之色。难以形容者。不亦心解矣乎。不宁唯是。又如喜则气
散。怒则气逆。思则气结。恐则气下。悲则气消者。亦可因其气之变。而拟议之也。何也。喜色油然以出。怒色
厉然以侮。欲色妪然以愉。惧色薄然以下。忧悲之色。瞿然以静也。色者气之华。有诸内必形诸外也。更进
而推展之。如经言风寒中于人。使人毫毛毕直。皮肤闭而为热。夫皮肤既闭。则其面色亦闭矣。此可因经
言皮肤闭。而知其面色闭。又可因病患面色闭。而知其皮肤闭。即可因面色闭。皮肤闭。而知其伤于寒也。
伤寒一日。太阳受之。太阳主表。其证头项痛。腰脊强。恶寒无汗。夫恶寒无汗。则其皮肤闭也可知。皮肤闭
则其面色闭也又可知。此可因恶寒无汗。而知其面色闭。即可因面色闭而知其恶寒无汗。又可因恶寒
无汗而知其头项痛。腰脊强。即可因头项痛。腰脊强。恶寒无汗。而知其太阳病。伤于寒矣。伤寒论云。太阳
病。或已发热。或未发热。必恶寒体痛呕逆。斯时也。未发热者。色或惨然而黑。此外寒之色也。已发热者。色
或怫郁而赤。此表热之色也。若未得汗。其色当闭。若已得汗。其色当开。若将汗未汗。则色当有闭而欲开
之象矣。匪直此也。更可因其赤色之微甚。而知其热之轻重。因其赤色之浮沉。而知其热之进退。因其赤
色之散抟。而知其病之聚散。因其赤色之泽夭。而知其症之成败。而凡六部十法。与夫四时五色。莫不可
推。伤寒如此。诸病亦然。神而明之。存乎其人。难以笔楮形容矣。
我认为脉理的奥妙，色理的奥妙更为深微。其中有些道理只能心领神会，难以用言语完全表达。然而病症不同，气色也应当有所差异。如果能推究并推广这一原理，扩充并充实它，触类旁通、由此及彼地延伸，那么即使是难以形容的情况，也可以推测和议论了。例如：风邪致病的面色当为青色，寒邪致病的面色当为黑色，暑邪致病的面色当为红色，湿邪致病的面色当为黄色。风邪导致脉象缓，寒邪导致脉象急，暑邪导致脉象虚，湿邪导致脉象涩。脉象缓的，尺部（前臂内侧腕后至肘横纹处）的皮肤也松弛舒缓；脉象急的，尺部的皮肤也紧绷拘急；脉象滑的，尺部的皮肤也滑利；脉象涩的，尺部的皮肤也滞涩不畅。脉象大的，尺部的皮肤也充盈隆起；脉象小的，尺部的皮肤也瘦减且气息微弱。综合观察面色、脉象和皮肤状态，就可以推断：风邪致脉缓者，应当面色青而皮肤舒缓；寒邪致脉急者，应当面色黑而皮肤紧绷；暑邪致脉虚者，应当面色红而皮肤瘦减且气息微弱；湿邪致脉涩者，应当面色黄而皮肤滞涩。像这样，风寒暑湿等难以形容的气色，不也就在心中豁然开朗了吗？
不仅如此，又如：喜悦则气机涣散，愤怒则气机上逆，思虑则气机郁结，恐惧则气机下陷，悲伤则气机消损。这些也可以根据气机的变化来推测面色。为什么呢？喜悦的面色是油然显露的，愤怒的面色是严厉傲慢的，欲望满足的面色是和悦愉快的，恐惧的面色是卑微退缩的，忧悲的面色是惊惧静止的。面色是气的外在荣华表现，内部有什么样的气机变化，必然会在外部显现出来。
再进一步推演，如经典所言：风寒侵袭人体，使人毫毛全部竖立，皮肤毛孔闭塞从而产生发热。既然皮肤毛孔闭塞，那么面色也会显得晦暗闭塞。这可以通过经典中提到的“皮肤闭”，来推知“面色闭”；也可以通过观察病患面色晦暗闭塞，来反推其皮肤毛孔闭塞；进而通过面色闭、皮肤闭，推知其伤于寒邪。
《伤寒论》记载：伤寒第一天，太阳经受邪。太阳主一身之表，其症状表现为头项疼痛、腰脊僵硬、恶寒无汗。既然有恶寒无汗的症状，就可以知道其皮肤毛孔闭塞；既然皮肤毛孔闭塞，就可以知道其面色晦暗闭塞。这可以通过恶寒无汗的症状，推知面色晦暗闭塞；也可以通过面色晦暗闭塞，推知恶寒无汗；还可以通过恶寒无汗，推知头项痛、腰脊强；进而通过头项痛、腰脊强、恶寒无汗等症状，推知这是太阳病（太阳经受邪所致的病证），且是伤于寒邪所致。
《伤寒论》说：太阳病，有的已经发热，有的尚未发热，但必定伴有恶寒、身体疼痛、呕吐逆气。在这个时候，如果尚未发热，面色可能惨白而发黑，这是外感寒邪的面色；如果已经发热，面色可能郁滞而发红，这是表热的面色。如果还没有出汗，面色应当显得闭塞晦暗；如果已经出汗，面色应当显得开泄明润；如果将要出汗但尚未出汗，面色应当呈现出由闭塞向开泄转化的迹象。
不仅于此，还可以根据红色的深浅程度，推知热邪的轻重；根据红色的浮沉位置，推知热邪的进退趋势；根据红色的分散或聚结，推知病邪的聚散情况；根据红色的润泽或枯槁，推知病情的预后成败。至于六部诊法、十种诊法以及四时五色理论，没有不可以推演的。伤寒病如此，其他疾病也是如此。能否做到神妙通达，关键在于医者本人，这很难仅靠笔墨文字完全形容清楚。
I hold that the principles of pulse diagnosis are subtle, and the principles of complexion observation are even more so. There are aspects that can be apprehended by intuition but are difficult to express in words. However, as symptoms differ, the qi and color (Qi-se) should also vary. If one extends this reasoning broadly, expands upon it, and applies it through analogy and gradual extension, then even those phenomena that are hard to describe can be speculated upon and discussed. For instance, the complexion associated with Wind pathogen should be Green; that with Cold pathogen, Black; that with Summerheat pathogen, Red; and that with Dampness pathogen, Yellow. Wind causes the pulse to be Slow (Huan); Cold causes it to be Rapid/Tight (Ji); Summerheat causes it to empty/Deficient (Xu); and Dampness causes it to be Choppy (Se). When the pulse is Slow, the skin at the Chi position (the distal forearm section from wrist to elbow) is also loose and relaxed; when the pulse is Tight, the skin at the Chi position is also tense and contracted; when the pulse is Slippery (Hua), the skin at the Chi position is also smooth; when the pulse is Choppy, the skin at the Chi position is also rough and obstructed. When the pulse is Large (Da), the skin at the Chi position is also full and protruding; when the pulse is Small (Xiao), the skin at the Chi position is also diminished with deficient Qi. By observing the complexion, pulse, and skin condition together, one can deduce: cases where Wind causes a Slow pulse should present with a Green complexion and loose skin; cases where Cold causes a Tight pulse should present with a Black complexion and tense skin; cases where Summerheat causes an Empty pulse should present with a Red complexion and diminished, weak skin; cases where Dampness causes a Choppy pulse should present with a Yellow complexion and rough skin. In this manner, the complex manifestations of Wind, Cold, Summerheat, and Dampness, which are otherwise hard to describe, become clear in the mind.
Moreover, consider that Joy causes Qi to scatter, Anger causes Qi to rebel upward, Pensive thought causes Qi to knot, Fear causes Qi to sink downward, and Sorrow/Grief causes Qi to dissipate. These changes in Qi can also be used to speculate on the complexion. Why? The complexion of Joy appears oily and radiant; the complexion of Anger appears stern and domineering; the complexion of satisfied desire appears warm and pleasant; the complexion of Fear appears thin and retreating; the complexion of Worry and Grief appears startled and still. Complexion is the external splendor of Qi; whatever exists internally must manifest externally.
Further extending this reasoning, as stated in the classics: when Wind and Cold invade the person, causing all hair follicles to stand erect and the skin pores to close, leading to heat. Since the skin pores are closed, the facial complexion will also appear closed and dull. One can infer "closed complexion" from the classic statement of "closed skin"; conversely, observing a patient's closed/dull complexion allows one to infer closed skin pores; and from both closed complexion and closed skin pores, one can infer injury by Cold pathogen.
According to the *Shanghan Lun* (Treatise on Cold Damage): On the first day of Cold Damage, the Taiyang channel (Taiyang Disease) is affected. Taiyang governs the exterior. Its symptoms include headache and stiffness in the head and neck, stiffness in the waist and spine, aversion to cold, and absence of sweating. From aversion to cold and absence of sweating, one knows the skin pores are closed; from closed skin pores, one knows the facial complexion is closed/dull. Thus, from aversion to cold and no sweat, one infers closed complexion; from closed complexion, one infers aversion to cold and no sweat; from these symptoms, one infers headache, neck pain, and back stiffness; and finally, from headache, neck/back stiffness, aversion to cold, and no sweat, one diagnoses Taiyang Disease caused by Cold injury.
The *Shanghan Lun* states: In Taiyang Disease, fever may or may not have appeared yet, but there is invariably aversion to cold, body pain, and vomiting/rebellion of Qi. At this time, if fever has not yet appeared, the complexion may appear pale and dark/black, which is the sign of exterior Cold. If fever has already appeared, the complexion may appear depressed and red, which is the sign of exterior Heat. If sweat has not yet been produced, the complexion should appear closed/dull; if sweat has been produced, the complexion should appear open/bright; if sweat is impending but not yet produced, the complexion should show signs of transitioning from closed to open.
Furthermore, one can judge the severity of Heat by the intensity of the Red color; the progression or regression of Heat by the superficiality or deepness of the Red color; the aggregation or dispersion of the disease by whether the Red color is scattered or condensed; and the success or failure of the prognosis by whether the Red color is lustrous or withered. All methods of the six positions and ten techniques, as well as the five colors corresponding to the four seasons, can be deduced in this way. This applies to Cold Damage, and similarly to all other diseases. Spiritual understanding and illumination depend on the practitioner; it is difficult to fully capture in writing.