How can you tell when Vegeta is fighting in super saiyan god or in super saiyan blue in the manga?
SSJG Vegeta has a black pupil in his eyes while SSJB Vegeta doesn't.Also,  the shading in case of SSJG is slightly darker than SSJB. However, it is slightly more difficult to see that. SSJG VegetaSSJB Vegeta