We know that the complexion of Lord Vishnu / Krishna is dark (shyam varna) but what is the complexion of Lord Shiva, dark or white?
Lord Shiva's Complexion was described in Chapter Four (Cancula's Salvation) of Shiva Purana Mahatyam in Shiva Puranam. You can see that from here.(Page 18)
She saw the three-eyed Mahadeva, the eternal, being served devotedly by Brahma,Vishnu and other gods.
He had the brilliance of ten million suns and was reverently served by Ganesha, Bhrngi, Nandisa, Virabhadreshwara and others.
His neck had a blue hue ; he had five faces, three eyes , the cresent moon as crest-ornament and his left hand was apportioned to Gauri , who had the brilliance of lighting.
He was white in complexion like camphor and wore all ornaments. Besmeared with white ashes all over the body and clad in white clothes,he shone brilliantly.
The woman Cancula became highly delighted on seeing Shankara.In her flutter of delight she bowed again and again to Him.
The complexion of Shiva is white. He is described as Karpura Gauram- white like camphor. But, the complexion of Maha-Kala and Kala Bhairava is Black, as they represent time and annihilation.
This may be of interest to you- http://pratyasha.deviantart.com/journal/Shiva-is-not-Blue-but-White-371562557
One of the common "śloka" chanted right after "Aarti" and It is found in Yajurveda, one of the four canonical texts of Hinduism is below one, in Praise of Lord Shiva
कर्पूर गौरम करूणावतारम संसार सारम भुजगेन्द्र हारम | सदा वसंतम हृदयारविंदे भवम भवानी सहितं नमामि ||
The first word in above sloka, describe the complexion of Lord Shiva.
कर्पूरगौरं (karpūragauraṁ): The one who is as pure/white as a camphor(karpur)
Ṛṣis of the Vedās were very explicit about the appearance of Rudra and the commonality with that of Śiva. While the first declaration to Rudra is seen in the Rig Vedā, the Saṃhitās of Atharva & Kṛṣṇa Yajur Vedās give utmost detail on His features and nature. To start with, Rig Vedā 1.43 – which is the first declaration to Rudra – says in hymn 5: “He is brilliant like the sun, dazzling like gold, and the best of the divine and of Vasu”. Across the Vedās, His form is Viṣvarūpam, meaning the cosmic form or the all-encompassing omni-form RV2.33.10,TS4.5.4,TA10.23.1, or Pururūpam, meaning multiform/multihued, with trayambakam, meaning three-eyes RV 7.59,TS4.5.4,AV11.2.2. At the same time, the Atharva Veda calls him “the thousand-eyed”AV4.28.3. On multiple occasions, He is referred as the one with Virūpākṣa, meaning the one with odd eyes TA10.23.1 or thousands of eyes VS16.8. Please note that the term trayambakam, with regard to appearance, means three eyes. With regard to nature, ambaka means Ritu (season) and Ambikā represents Autumn or harvest season. Amba+ka also means mother and sister. Both Śrī Rudram and Śatarudrīya describe a furious form emerging out of Prajapati. This anger is called Manyu, the ferocious aspect of Rudra with a hundred head, a thousand eyes, and thousands of weapons. This all-encompassing form of Rudra was very difficult to iconify into sculpture or painting, hence after Nārāyaṇa Sukta and Śrīmad Bhagavādgita, Viṣṇu’s Viṣvarūpam took high prominence in its depiction. Alongside Rudra, Soma and Prajapati shared the title of Viṣvarūpam, but Varuna is also addressed in a similar way RV7.34. When it comes to hue or color, He is Kṛṣṇapingala, meaning with tawny or orangish-yellow skin RV2.33, with arms shining like gold, नीलग्रीव/शितिकण्ठ blue/white neck VS16.28 and bluish belly AV15.1,VS 16.7,KYV4.5. In contradiction, He is also addressed as शुक्र, meaning clear/white/opaque RV2.33 – hence the name śukreśvara linga of Varanasi. But how does one justify so many hues/colors? He is called Multihued and Pururūpam. His hair is called kapardi, meaning knotted/braided locks of hair RV1.114,AV 2.27. Rudra, in the Vedās, is associated in deep conjunction with Soma KYV 7.1,VS16 and Agni as one of his natures or epithets, and in several occasions with Surya. Similar to trayambakam or Virūpākṣa, there is a celebrated title “Somasuryagni Lochanaya“, meaning the one with Soma, Surya and Agni as his three eyes. Atharva Vedā 15th Kanda 18th Prayāya, famously known as Vrātyas Suktam, says “oh Vrātya, as for this right eye is the distant Sun/Āditya, so for the left eye is the Moon/Soma”. But what about the Agni of the 3rd eye which burnt Kamadeva? There is no direct declaration attributing the 3rd eye as Agni. However, Śrī Rudram of the YajurVedā urges Rudra’s missiles not to hit us. The same Vedā urges Agni – heat of those missiles – not to harm us, but be auspicious for us TS 4.61. Since we have described various contradictory features, attributes and forms, how can one visualize an image of the one who is called Viṣvarūpam/all-encompassing omni-form – who is but an enigma – especially when Vājasaneyi Saṃhitā 16.44 says “homage to the one who is in tempest, storms, in the hearts (Sun), in whirlpools, in deep wells and in the very abysses”? The first declaration of Rudra in the Rig Vedā, then the details in the Yajur Vedā and the Atharva Vedā, gave rise to Svetasvatara Upaniṣhad (one among the 18 primary Upaniṣhads), which says in Chap 3, sloka 11:
सर्वानन शिरोग्रीवः सर्वभूतगुहाशयः । सर्वव्यापी स भगवांस्तस्मात् सर्वगतः शिवः ॥ ११॥ All (सर्वा) heads, necks/faces (शिरो + ग्रीव) are you, as you are dwelling in all (सर्व) beings and their cores/hearts (सर्वभूतगुहाशय)| You are omnipresent/all-pervasive (सर्वव्यापी) in all divine forms (भगवांस्तस्मात्), all-encompassing in all (सर्व+गतः) Please note: शिर+स्तस् means forms of heads, and भगवां+स्तस् means divine forms. Svetasvatara Upaniṣhad 3.11
Please Note: RV = Rig Vedā, KYV = Kṛṣṇa Yajur Vedā, TS = Kṛṣṇa Yajur Vedā Taittirīya Saṃhitā, VS = Sukla Yajur Vedā Vājasaneyi Saṃhitā, TA = Kṛṣṇa Yajur Vedā Taittirīya Aranyaka, Atharva Veda = AV
For further details please read: http://sanatanadhara.com/ishwara/siva-rudra-linga/
we are human being and always like to see god in same form as human being. shankar portrait as human being but shiva is in form of shiv liga, which represent universe or shape of universe or shape of energy, and major part of universe is emptiness. and this emptiness is black in color.
worship of shiva is worship of emptiness or align with universe or harmonize with existence.