Were there any aircraft in solid upper and lower colors? Without all that mottling I mean. Thanks.
Not sure about solid except for maybe night fighters but some had solid demarcation between upper and lower. For example this BF-109
Bf109 G-6/AS (7./JG1), this 109 is complete in Lightblue RLM76.
So if you want to do Luftwaffe fighters without mottling you should generally stay in the time period BEFORE summer 1940.
There are of course exceptions, several are mentioned above, further well known examples that are common as decal options in kits are JG 54 aircraft from the Eastern Front, both FW-190 and Bf-109.
If you include the Mediterranean Theater, there were certainly several types of aircraft that were just grey brown on top and light blue underneath.