spots, the pathognomonic enanthem of measles, begin as small, bright red macules that have a 1–2-mm blue–white speck ...
[accessmedicine.mhmedical.com]
On mucous membranes, Koplik's spots (tiny bluish-white papules with erythematous areolae) may develop.
[patient.info]
It is characterized by a prodrome of fever (as high as 105°F) and malaise, cough, coryza, and conjunctivitis -the three “C”s -, a pathognomonic enanthema (Koplik spots) followed
[cdc.gov]