In the form of Ultra Instinct -Sign-, Son Gokou has a few major differences than his normal form. In this form, Gokou has silver eyes rather than his black eyes, his hair slightly changes, almost becoming of the style of his Super Saiyan form, his aura becomes a flame-like blue, and his body gives off heat.
Because of the explosion of the Genkidama, the energy of the attack clashed with Son Gokou's energy, causing Gokou to break his shell of deep potential. This allowed him to receive a power-up and master Ultra Instinct temporarily. In his battle with Jiren, Gokou was able to match Jiren in power and speed, though the Genkidama was not able to damage the mortal of God of Destruction level. However, Gokou's time in the form is temporary. He later was able to transform back into this state during his battle with Super Saiyan Kefula because he power was equivalent to Gokou's Genkidama against Jiren.