For those who are new to Kickstarter: for now you just choose the level of pledge you like. Size and colour choice only happen at the end of the campaign once the project is complete and successful.
Pledges can be changed, upgraded or cancelled right up to the final day of the project.
You are only charged at the end of the campaign and if the campaign pledge target is achieved.
Don't see the answer to your question? Ask the project creator directly.