For oil paint swatch database, I used the following 8 tubes of paint from Old Holland brand based on Claude Monet’s palette:

Scheveningen yellow lemon (Pigment: Monoazo PY3)
Cadmium yellow medium (Pigment: Cadmium zinc sulphide PY35)
Scarlet lake extra (Pigments: Anthanthrone PR168 - Quinacridone PR209)
Alizarin crimson lake extra (Pigments: Quinacridone PV19 - Anthraquinone PBR23)
Cobalt Blue (Pigments: Oxides of Cobalt and Aluminium PB28)
French ultramarine light extra (Pigments: Synthetic ultramarine PB29 - oxide of cobalt and aluminium PB28)
Viridian green deep (Pigment: Chromium hydroxide PG18)
Mixed White (Mixed white number 2: zinc and titanium)

From the producers website: "Lake" means transparent glazing colours, "Extra" means traditional colour made from lightfast pigment.

Please note that I have no affiliation with this brand. I chose it because of its consistency and pigment quality, based on recommendations from artists teaching at the Museum of Fine Arts of Boston.

these paints were mixed together to cover the color gamut. Mixtures with 2, 3, 4, and even a few 5-paint ingredients were made. For each mixture, all the ingredients were weighed carefully to achieve the desired proportions. The Mixed White paint (A mixture of Zinc and Titanium White) was added to each mixture to lighten up the created hues in different steps. Black paint was avoided and dark values were created through mixing complementary colors.

My objective was to make paint mixtures with known concentrations. Therefore, for each mixture, comprising paint ingredients are weighed one by one on a disposable non-absorbent laboratory sample paper. The following scale was used for all weight measurements: Smart Weigh Pro Pocket Scale, readability: 0.01 gram. The ingredients are then mixed patiently and thoroughly using a metal mixing knife. The base for the swatch is a sheet of Arches oil paper (100% cotton, 300 gr) that has been divided using masking tape into 20x20 squared millimeters spaces. T he mixture is spread on the designated square space by the edge of a flat metal painting knife so that the patch has a smooth surface finish. Negligible amount of paint will be left on the masking tape. When all square spaces on a sheet of paper are filled, the paper is stored in a closed plastic container, and left to dry for a few weeks, away from possible dust or contamination. Once dried, the masking tapes are removed to reveal a tidy sheet of paper containing 35 patches bordered by the white of the paper, as shown in the picture (click on it to enlarge). Each patch of color is about 20 x 20 mm (~ 1 x 1 inch) large and about 2 mm (1/10 inch) thick.

Here are some quick notes for the attention of the non-color scientist reader. My source for the information is the following book: "Vision and Art, The Biology of Seeing" by Margaret Livingstone, ISBN 978-0-8109-9554-3. It is a very interesting and informative book for artists.

Light, in form of electromagnetic waves, come down from the sun (and other illumination sources) to us. Each electromagnetic wave can be characterized using its "wavelength". (Because we like to assign a "number" to everything so we can work with them easier). Those electromagnetic waves that have a wavelength between 400 nm and 700 nm can be detected by human eyes and can be interpreted in our brains as "colors". Therefore, we refer to the range of 400 nm to 700 nm as the visible spectrum.

For example, an electromagnetic wave with wavelength equal to about 500 nm is usually interpreted in our brain as color green. The reason for this "usually" is that, it depends on the beholder! We are all different in terms of light receptors that we have in our eyes and the way our brain interprets the signals coming from these receptors. That's why a green leaf can look brown to a some color-blind people. To solve this problem, the International Commission on Illumination (CIE) came up with a standard observer. Color scientists use this standard observer in their calculations for consistency. The rendered image below shows the associated color that the standard observer sees by looking at light of different wavelengths in the visible spectrum. We can understand from the image that when we see an object as "green", it means that the object is reflecting mostly the light at wavelengths about 500 nm to 550 nm.



When some rays of light from an illuminant (sun, light bulb, etc) hits an object, the object transmits or absorbs some parts of this light, and reflects the rest of it to our eyes. Therefore, the light that reaches our eyes varies depending on the object that reflects it, but also the type of illuminant. Once again, for consistency reasons, the CIE defines standard illuminants. For example, the illuminant D65, which is used in the calculations in this work, is defined to resemble average daylight. Here is the explanation from CIE (source: http://www.cie.co.at/publ/abst/s005.html):

CIE standard illuminant D65:
(Joint ISO/CIE Standard, ISO 10526:1999/CIE S005/E-1998, CIE Standard Illuminants for Colorimetry)
"This is intended to represent average daylight and has a correlated colour temperature of approximately 6 500 K. CIE standard illuminant D65 should be used in all colorimetric calculations requiring representative daylight... Variations in the relative spectral power distribution of daylight are known to occur as a function of season, time of day, and geographic location. However, CIE standard illuminant D65 should be used pending the availability of additional information on these variations."

For each of the color swatches, I have included in the Swatch Specifications section a plot that shows reflectance factor of the color at different wavelengths. A light spectrum is put as the background of the graph. An example will show you how to interpret the graph: Consider the first color patch. It is made of 1 part Lemon Yellow + 1 part Scarlet Lake + 38 parts White. We can see in the reflectance graph that this color patch is reflecting mostly the light with wavelengths greater than 600 nm (the peak of the graph), which corresponds to the orange color of the patch as also seen on the background rainbow image. Reflectance at wavelengths corresponding to the constituing Yellow and Scarlet red paint is the highest. In general the reflectance graph for this patch goes through high values of reflectance factor, because high amount of White paint has lightened up the color (Higher reflectance factor means more light reaching to our eyes, which means "lighter").

I used a sphere spectrophotometer, namely the X-Rite Color i7 instrument for the measurements. Full technical specifications and details can be downloaded in the Publications section. In summary, I calculated the X Y Z tristimulus values using the Reflectance factor at 400 to 700 nm, in 10 nm steps, CIE 2nd observer, and CIE D65 illuminant. The colors shown in this website are created by inputting my data into the HTML RGB function. The L* value is used here to represent the lightness (gray vlaue) of each swatch. Appointments to view the actual swtaches can be arranged, please contact me for more information.

You can consult a general view of the palette here. If you click on any of the colors, it will take you to the detailed specifications of that color. Full details can be downloaded in the Publications section.

You can find here the details for each swatch color