## 1 Introduction and Objectives  
### Background  
Currently, advancements in lighting technology are markedly enhancing the energy efficiency promoted by LED light sources, with a primary focus on reducing energy consumption and corresponding CO\({}_{2}\) emissions [1]. Nonetheless, this progression frequently overlooks the implications of this type of luminiares on color appreciation [2], human health effect [3, 4], and well-being [5]. As posited by various researchers, lighting design in architecture should encompass considerations beyond the mere distribution and quantity and light, extending to its quality [6, 7, 8], thereby fostering a comfortable scenario for users and a proper perception of the environment. Most of the lighting systems currently available on the market employ LED technology, which generates a distinct spectral distribution compared to older sodium-vapor, halogen, and fluorescent lamps, resulting in a noticeable variation in color fidelity and chromaticity. Specifically, LED lamps exhibit significant variation in their chromatic perception due to the peak located in the short-wavelength spectrum [9]. LED lamps are cost-effective and provides a higher luminous efficacy in comparison with their predecessors. In addition to the previous observations, the cutting-edge technology of LED lamps offers an interesting solution for improving color perception in architectural environments:multichannel luminaires. This type of light source, usually controlled by a DALI language, adapts the spectral power distribution (SPD) of the lamp, with the aim to render, in an optimized way, the colors of unique spaces of architectural heritage. The multichannel luminaire, composed of a set of LED lamps with different peaks and bandwidths in the visible range, can mimic the spectral distribution of daylight with noticeable accuracy, thus improving the light quality and the object's appearance [10]. Given this context, the lighting design of museums, churches, and similar heritage buildings acquire a new tool for improving the color perception of inner spaces, creating unique atmospheres depending on the designer's intention [11]. Accordingly, by modifying the Correlated Color Temperature (CCT), which can be deduced from the SPD of the light source, the chromaticity of the different hues of paintings can be adapted to different scenarios, changing, therefore, the observer's perception [12]. As an example, multichannel luminaires can render the spectral distribution of a real flame, with the aim to reproduce paintings and frescoes as ancestral observers saw such elements [13], opening a wide range of potential solutions with this new technology. The scenario described underscores the necessity for a precise evaluation of the effects induced by these new lamps on color rendering [14], since, as described above, this technology is currently used in heritage environments, where the hue fidelity and chromaticity discrimination are crucial for a suitable understanding of paintings, frescoes, and altar pieces. There are several procedures to define the color rendering provided by a light source from a quantitative approach. One of the latest and more widespread methods for fully describing the color perception is TM-30-20, defined by the Illuminating Engineering Society of North America (IESNA) [15]. This procedure contrasts, in the CIE Lab color space, the results for 99 hue samples, setting a continuous illuminant reference which is adapted depending on the CCT of the studied light source. IESNA is currently advocating for the adoption of this method among lighting manufacturers [16]. Moreover, the Daylight Spectrum Index (DSI) [17] is a novel concept which offers a different approach for defining the color preference, using SPD fitting instead of the analysis of hue sample deviation within a color space. This innovative concept assesses the color similarity provided by a lamp in comparison with daylight, contrasting the SPD of both sources, depending on the color sensitivity functions of human vision.