Visual Journal : Investigating colour in relation to form

I have began my visual journal by investigating one of the key theories represented in my essay - how the relationship between colour and form shapes the communication of a subject.

To do this, I choose simple geometric shapes and experimented with how changing the colour in these shapes or around them influenced their meaning - demonstrating the importance of colour in the aid of communication. 

This investigation has led me to a number of questions, mainly surrounding semiotic theories... 

The lemon and the lime - they are natural forms, therefore our understanding of their shape and colour is innate. However, the plus and circle shapes are often symbols that we would understand through learned conventions based on our cultural background - therefore which signs/symbols are innate and which are learned? Is our understanding of the sun and the moon, one being a yellow circle and the other a white circle surrounded by darkness, innate or learnt?  (because the sun isn't really a yellow circle in the sky!)