Is ghusl obligatory for a suspicious wetness that has no color, no smell, and no viscosity?

As long as you are ignorant of the true nature of the wetness you saw—whether it is maniyy (semen), madhiy (pre-seminal fluid), or something else—you have a choice. If you wish, you may consider it madhiy. In that case, your prayer is valid if you have washed the impurity of the madhiy from your body and clothes, performed ablution, and prayed in clean clothes. If you wish, you may consider it maniyy. In that case, you must perform ghusl (definition) (ritual bath) for janabah (definition) (major ritual impurity) and repeat the obligatory prayers you performed before performing ghusl, according to the view of the majority, which is what is issued as fatwa (definition) by us. It is also said that you are not obligated to repeat the obligatory prayers you performed before performing ghusl.