A short example:
I created a field named "Text" for the layer "Vertices" and put a bunch of numbers in it. I could have put the words for the colors I wanted to use. I then selected the Categorized Symbology and picked the Value "Text" from the list of fields in the layer.

When you Classify the group it will be a random color ramp. Then you can change the color of the "Value" that you want.

Below I changed all of the dots with the value "33" to a brown.

If you do add a field just for color you could just name the field "color" and put values like green, pink, red in there. That would make it easy to remember.

If your data can be posted, feel free to post and I'll take a look.
Good luck

A short example:
I created a field named "Text" for the layer "Vertices" and put a bunch of numbers in it. I could have put the words for the colors I wanted to use. I then selected the Categorized Symbology and picked the Value "Text" from the list of fields in the layer.

When you Classify the group it will be a random color ramp. Then you can change the color of the "Value" that you want.

Below I changed all of the dots with the value "33" to a brown.

If you do add a field just for color you could just name the field "color" and put values like green, pink, red in there. That would make it easy to remember.

From your data:

Can you explain the 2 fields that should be linked between the rivers and lakes?

['fid', 'FID_ca_str', 'SUB_BAS', 'MAJ_BAS', 'MAJ_NAME', 'SUB_NAME', 'SUBBAS_ID', 'TOBAS_ID', 'Strahler', 'A_Strahler', 'RASTERVA_2', 'RASTERVA_1', 'path', 'BASIN_ID', 'AREA_SQKM', 'layer', 'path_2', 'color']