Indian Red and Venetian Red are both very opaque, granulating earth reds made from synthetic iron oxide (PR101). Indian Red is more violet-toned (earth maroon), diluting to dusty pink; Venetian Red is more orange-toned (earth scarlet), diluting to peach. In the versions I used, Da Vinci Indian Red was significantly more granulating than Winsor & Newton Venetian Red, especially noticeable in masstone.
Color Mixes
Raw Sienna (PBr7)
These mixes are fairly similar though the VR ones comes across as orange, whereas the IR ones come across as being more muted and soft.
Ultramarine Blue (PB29)
The brown mix (second swatch for both of these) strikes me as reading more like a “brown” for the VR mix, whereas it looks more violet for the IR mix. The other mixes don’t look as different.
Phthalo Blue Red Shade (PB15:1)
VR is a complement of PBRS and makes a granulating neutral black/gray. It also makes a fairly middle brown. The bluest mix looks a lot like genuine Cerulean to me (a bit grayer). All the IR mixes are a bit more violet, making reddish browns. The more ‘neutral’ mixes are very soft and never quite read as gray; they are too color-separating and either warm or cool.
Cerulean Blue Genuine (PB36)
These mixes are fairly similar; soft dove grays with color-separating blue granulation. VR makes a cooler brown and IR makes a more violet brown.
Phthalo Turquoise (PB16)
This is one of the mixes that looks most different to me. The cool brown mixes with Phthalo Turquoise + Venetian Red look like Raw Umber to me, very useful cool browns. It can also make a Burnt Umber-ish looking color. Again, the IR mixes all have more of a violet tone, and because they are more color-separating they look more like “blue and Indian Red at once” instead of an even mix.
Phthalo Green (PG7)
I thought that since Phthalo Turquoise neutralized Venetian Red, then Phthalo Green might neutralize Indian Red, but it didn’t really work out that way. I didn’t like any of these mixes.
Conclusion
Some of the differences in these mixes are due to the difference in hue (i.e. the VR ones looking generally more orange-toned and the IR ones looking generally more violet-toned; VR muting Phthalo Blue RS and IR muting Phthalo Green). Other, harder-to-articulate differences appear to be due to differences in granulation, which may vary more with brand. I found that WN VR, being generally less granulating, made more integrated mixes, while DV IR, being more granulating, made more color-separating mixes and more of what Liz Steel calls “pigment parties.” Which you prefer will depend on your painting style.
I think Indian Red is more unique. I don’t really know of another color that does what it does: making a range of wonderfully violety browns. It is a perfect color match for certain types of red rocks, and that’s a hard color to match without it.
Indian Red is also texturally unique. In her video on Venetian & Indian Red, Denise Soden gushes about how Indian Red looks “just so soft,” and that’s exactly it. I don’t know what gives it that magical softness, and nothing else quite has it. But: as with many granulating colors, I find it has a very distinctive look in mixes and always seems to be trying to steal the show.
By contrast, the VR, to me, feels less unique and special, but has more versatility. It makes a wider ranges of mixes that make me think, “Ooh, I know how I could use that.” It’s capable of mixing browns that simply read as brown, whereas Indian Red’s browns always scream “I was mixed with Indian Red!”
I don’t have a simple conclusion to which I prefer, because it depends on the circumstances. I feel like VR may be a more useful everyday mixer for me, but there are some circumstances (e.g. in the Desert Palette) where IR is the only way to go.