Changes in saliva colour noticeable in the evening

Hi members,
I have noticed that my saliva has gone darker in colour and is noticeable in the evening. Is this due to Pre Diabetes or Diabetes?

I am brushing my teeth in the evening and morning. I do sometimes forget in the evening. could the symptoms be related to gum disease?

I was also told it could be thyroid gland problems. I don’t have any symptoms other than change in Sylvia. Advice will be greatly appreciated.