In addition to adopting and colouring the woodcuts mentioned below or should you prefer something more immediate I heartily recommend you get to grips with Pinterest. This is a free web and mobile application which offers an online facility to create your own visual themed boards.
It has a search facility to scour the boards of other people or you can upload your own images, when you see an image you like you ‘pin’ it to the board you have allocated. You can then share your boards with others, once you have pinned some images the site soon recommends pins based upon your searches, it is fun and immediate, you can easily gather hundreds of themed images in a short time.
I have found these boards really useful as a quick visual tool for colour combinations. The boards I have created on this subject are a collection of coloured woodcuts and a collection of photographs of Landsknecht re-enactors, I have found these have helped me to better appreciate some of the finer details of equipment, palette and dress.
You can view my Pinterest boards and re-pin individual images or the entire boards via the links below, happy pinning !