A few clarifications here (As it is a Religious topic, all are IMHO, but i’ll provide cites to whatever i say if you need):
1> Hinduism is not a code of conduct for the society but rather an guide to oneself.
2> The word Hindu means, the people who lived beyond (east of) the river Indus. It has no relevance to faith or beliefs or anything else. In fact none of the “hinduism” books calls anyone hindus.
3> The concept of God as described in Hinduism is thus : God is infinite and omnipotent, and humans cannot realize God because through their 5 senses. However, any representation of God is valid and everyone should decide based on their personality the form of God they like. Even if they think their particular version of God is correct and all others are wrong, they are right. So Christians, Muslims and Jews are Hindus too.
Not having any representation of God is fine too. God is not a definition imposed on anyone but rather a discovery within themselves. There are different paths to God namely - worship of God’s representation, Doing your work whole heartedly (Karma) and other methods. Everyone has to decide for themselves what works best for them. There is no one size fits all approach.
4> Coming back to many arms and colors. These are again a part of mythology and representations. People generally are awestuck by something which is fear arousing (the different representations of Kali - the black goddess), filled with love (the baby krishna) etc. etc. The many arms were added to make them appear frightening or having different powers.
Shiva is blue because he is bitten by snakes and does lot of opium and stuff. Krishna is blue because he was bitten by a snake when a kid and survived. Krishna has rampant sex when a youth. The Gods in heaven keep drinking lots of alcohol etc. etc. Representations of Gods keep playing jokes with each other, etc. etc. You can make fun of Hindu Gods, and infact they are often ridiculed. Krishna is ridiculed for running away from a fight (Taunted as : The running away scared wrestler). Shiva is one who gets fooled all the time in mythology and dresses rather scantily and is insulted by his in laws. etc. etc.
The point here is that the representation of Gods are as fallible as humans. Again, there is no restriction to the properties of God you can think about but still that is your God. It is left to individuals to decide how their God is.
Another thing central to hinduism (philosophy) is the concept of observer and the observed. Its said that everyone is a creator if their own reality. Also, the universe exists because you exist and you choose to observe.
Since every representation of God is valid, Hindus historically did’nt deem necessary to convert people. Also, you cannot convert to Hinduism, there is no equivalent of Church, Mosque, etc. in Hinduism (that is you don’t ever have to go any temple to prove u’r religion), etc.