A photo book is a great idea.
Yes bright colours are great for dementia. Our uniforms are rainbow coloured for this reason!
Definitely label the photos with name and relationship. If the care staff have to ask "who is that?" and the person with dementia doesn't remember, it can remind them that their memory is failing them and it can make them feel frustrated and upset.
I find older photos are better. Short term memory is usually the first to go, whereas they remember things from decades ago for a lot longer. So for eg photos of you and your mum when you were little.
Houses, cars, and pets are good too. I have a resident who has such severe memory loss and confusion and cannot remember almost anything at all, but show her a photo of her old holiday house, and she can tell you in vivid detail about the house, down to paint colour, architraves, furniture, and plants in the garden. It also brings back lovely memories of her husband because he built the house himself.
Places and landmarks that are special to them are good too. For eg I have a resident who grew up in Holland, and a generic photo of the Rhine brings back stories of how he used to swim in it and teach younger kids how to swim.
I hope that helps.
Also another thing that brings familiarity and memories is music. If you can provide copies of or a list of specific artists and songs, that is very helpful. It's so amazing when even a largely non-verbal resident hears a song from their youth and starts singing along with the full lyrics!