Hi
This is the typical maroon tint of a natural dye called porphyrin, which is characteristic for the onset of a urinary tract infection (both bacterial or sterile) and for any sterile cystitis flares.
Blood can be present but doesn't have to in every pee. It takes a whole lot more of it than you think to actually discolour urine. Blood is usually a much brighter red to pink shade, drying into mid-brown tones but you rarely see it in infectious pees.
For more information on sterile cystitis, you may find this link here helpful:
Wiebke's Guide to Pees and Stones
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